Potentially deadly complications for your child. Nightly news begins right now. Announcer from nbc news World Headquarters in new york, this is nbc nightly news with lester holt. Good evening. Republicans voting in four primary and caucus states tomorrow may still be frying to process the takeaway from last nights debate in detroit. Besides the schoolyard bickering and taunts that weve now come to expect, the debate did resurface some inconsistent positions on key issues by frontrunner donald trump, and he followed that up today with another surprising aboutface. While Trumps Campaign has proven impervious to missteps its yet another reminder of how his candidacy continues to confound his critics and opponents. Nbcs katy tur starts us off tonight. Reporter donald today. President ial. Ill be so president ial that you people will be reporter who is the real donald trump . A true conservative or a chameleon . Ive never seen a successful person who wasnt flexible. You have to be flexible because you learn. Reporter the frontrunner still throwing jabs at his opponent. You defrauded the people of florida, little marco. Breathe, breathe, breathe. Reporter and still hard to pin down. So how is any of this telling it like it is . Well, in afghanistan i did mean iraq. I think you have to stay in afghanistan for a while. Reporter trumps flip flops, headspinning, for giving syrian jeff reese asylum and then against it and for taxing companies who move jobs overseas. What are we not going to eat anymore, oreos reporter but against criticism that his own line of ties and shirts are made abroad. They devalue their currencies, and they make tim possible for clothing makers in this country. Reporter last night defending targeting the families of terrorists and waterboarding saying the military will follow his orders. They wont refuse. They are not going to reporter but against it today, telling the wall street journal, quote, i will not order a military officer to disobey the law. To a great extent a lot of people are voting for him without knowing what he might do as president but basically saying this is someone i like. Reporter today mitt romney saying he couldnt hold back his disdain. But the time came when Donald Trumps outrage had reached such a level that i simply had to speak out. Reporter and although his opponents claim trump has insults instead of policy, will lose to Hillary Clinton, destroy the party and perhaps the country this is a time for seriousness on thesishous. You have yet to answer a single serious question about any of this. Reporter none of them refused their eventual support. Ill support the republican nominee. Yes, because i gave my word that i will. I will support whoever is the republican nominee for president. Reporter donald trump was supposed to speak at cpac tomorrow, the conservative gathering instead abruptly for a rally in kansas tomorrow. So far this Campaign Season hes only received mixed receptions at similar gatherings. Lester. Katy, thank you, and all this nastiness could make it awkward for trumps remaining rise. To support him if hes the nominee as you heard them promise. They all, of course, hope it doesnt come to that, but they may have less than two weeks to stop his momentum. Nbcs Hallie Jackson cpac with more. H ha llie. Reporter good theres a lot of talk about that never trump movement, but a better name for it for some may be never until november as all the antitrump candidates pledged their loyalty to donald trump if he is the nominee. Still, all three will fight ferociously over the next 11 days to try and prevent that from happening. Short term ted cruz is looking at louisiana, libertarianleaning maine and is hoping for a strong showing in kansas, too, but so is marco rubio with three stops in that state today alone. Both of them, plus john kasich, hopes michigan could be a try and topple trump, but the more important date, thats march 15th, the home state showdown, rubio has to win florida, kasich has to win ohio. If they do and pick up valuable delegates, then everybody stays in the race since all three see narrow although unlikely paths to victory between now and the summer, thats why you shouldnt expect to see them team up to try and take down trump tactically. But if trump wins both florida and ohio, it looks like just a matter of time before he hits that magic number he needs, 1,237 delegates, so march 15th, either trump is the presumptive nominee or we look headed to a contested convention in cleveland. For people who cover politics its catnip, but for the gop it could be a watershed moment that reshapes the future of the party, lester, and one other note for you. Late tonight here at Cpac Ben Carson formally suspending his campaign, officially making it a fourman race. Lester . Hallie jackson tonight, thank you. The latest jobs report is out and last expectations, the u. S. Added 242,000 new jobs in february, beating economist estimates by about 50,000. The Unemployment Rate remained stead the at 4. 9 . Much of those new jobs were added in health care, retail and bars and restaurants. Jobs are exactly what Hillary Clinton focused on today in michigan, but once again it was her private email server that her critics seized upon. Clinton is eager to move forward beyond the controversy, and she hopes that records from a former aide granted immunity will be able to do it. Nbcs Kristen Welker explains. Reporter with the michigan primary on clinton is in detroit today calling for sharp cuts in tax breaks for companies outsourcing jobs overseas. So michigan proves every day that American Workers are the best in the world. All they need is a fair chance. Reporter but her private emails large. Former clinton staffer bryan pagano who help set up her private account was granted immunity to talk to the fbi selling while there may have been routine phishing attempts there is no evidence that the emails were hacked cnbcs john harwood. Im happy now that everybody has been cooperating and giving information. Reporter would you concede that you and the people who worked for you at state department were sloppy in the way you handled top secret information . No, no. Reporter today donald trump saying the emails are Bernie Sanders only hope. The only thing that can save him if is something happens to hillary with regard to the emails. Reporter meanwhile, sanders kept the focus on their trade differences. Hillary clinton was on the other side of many of these trade agreements supporting nafta. Reporter clinton dismissed the criticism and saved her sharpest attacks for last nights gop debate. Should be at the top of any list that anybody running for president has was thought. Reporter clinton and sanders will face off at a debate in sunday. Expect sanders to again be in attack mode, but secretary clinton has to be careful not to hit back too hard to alienate his supporters, the very voters she will need if she does make it to lester . Kristen, thanks. After nearly 22 years, the o. J. Simpson case is back in the headlines with a surprise revelation that a knife was found years ago on simpsons former estate. This potential evidence was kept out of investigators hands until about a month ago. Tonight the knife is being examined by police, but sources are already casting doubt about whether it could actually be the murder weapon used in the double murder. Nbc dateline correspondent Josh Mankiewicz has more on the new twist in this still open case. Reporter today the lapd confirmed that had this knife in his possession for some time, even though investigators were only able to take possession of it this past january. Its been submitted to our lab. They are going to study it and examine it for all forensics, including serology and dna and hair samples, and that is ongoing as we speak. Reporter the story police are being told involves construction workers finding the small folding knife while they were doing work on o. J. Simpsons former property in l. A. After it was sold to a new buyer. They gave it to a now retired Police Officer working off diet at a move shoot across the street. He claims he was told the case was closed and so he hung on to the knife for a number of years. It was brought to our attention that this retired overs had an item that was believed to or that was possibly taken from or recovered from the Rockingham Estate back in the 90s. And recovered that from him. Stand and face the jury. Simpson was tried for the 1994 knife murders of his exwife nicole and her friend ron goldman in a case that seemed to be on every tv set in america. In an interview airing this sunday, former prosecutor marcia clark speaks to dateline. Right off the bat thereto was a sense of loyalty of investment in protecting an africanamerican icon who had made it. He was successful. He had made it. They did not want to see him taken down. Not guilty. Reporter the defendant was acquitted despite significant evidence against him, but no murder weapon was ever found and now the fx series the people versus o. J. Simpson has surprised in the rightings as many people seem to want one more dose of a story that wont go away. This is not the first time a knife has made it to police. Other knives have been submitted over the years, but this is the from the simpson property. Ies in ninemonth criminal trial is over, he was acquitted. The civil trial is over and he was found responsible. I dont see anyone prosecuting o. J. Simpson for anything related to this case again. Reporter ton multiple sources are expressing skepticism about the knife and about its possible value in the case in part because it may physically be too small to have left wounds on the victims and in part because its so tantalizing, because it surfaced at precisely the time that this case is once again on everyones lips. Lester . Tonight, thank you. And a programming reminder, date line versus o. J. Simpson, what the jury never heard this sunday at 9 00 p. M. Eastern. Closing arguments wrapped up late today in the erin andrews civil trial. The Sports Reporter is demanding 75 million after she was secretly filmed in a hotel by a man later convicted of stalking her. And beginning monday the case will be in we get more from nbcs morgan radford. Victim. Reporter erin andrews legal team making its last attempt to convince a jury that shes still emotionally damaged from the stalker video that was secretly recorded eight years ago at the nashville vanderbilt marriott. The trauma happens day after day and its never going to stop. Lawyers arguing that the former owner and management company, along with convicted stalker michael barrett, should pay andrews 75 million for Emotional Distress and loss of privacy. Earlier this week andrews says shes still haunted by it daily. Its going to be on the internet until i die. Reporter but the hotel says it did not give barrett her room number and was manipulated in giving barrett the room next to andrews. Mr. Barrett is a criminal, a stalker, counsel is trying to tie my client to the client but had nothing to do with that guy. Reporter there were several pieces of evidence all leading up to this. Its all left up to the jury, seven women and five men. They are given guidance on how to assess damage but no fixed formula on how much to award, especially when it comes to emotional injuries. Even if a jury does side with andrews, they might not agree with the 75 million shes asking for. I work for a moving company. I make 50 grand a year. Thats a lot of money. Ill give her 50 grarngsd you see what im saying . The jury is going to put their perspective of what money is on this case. Reporter the jury has chosen to deliberate on monday and court will resume at 9 00 a. M. Now, if they do choose in favor of erin andrews that means they will have to specify the amount of damages. Lester . Morgan radford in nashville, thank you. A newly unsealed autopsy report shows Bobbi Christina brown had several drugs in her system about she a bathtub but it does not make clear if her death was a suicide, accident or homicide. Morphine, alcohol, prescription drugs and alcohol were all found report. The daughter of the late Whitney Houston and bobbi brown was in a coma for nearly six months. She died last july and today. The city of flint, michigan has finally put into action a plan to replace all of its lead pipes. The work began on the first of many homes to lines with new copper lines. The mayor says the 55 million project could be completed been a year. A costcutting measure back in april 2014 led to flints water beinging tainted with lead. Still ahead tonight, peanut allergies and the new and unconventional approach that might folks out there whose diabetic nerve pain. Shoots and burns its way into your day, i hear you. To everyone with this pain that makes ordinary tasks extraordinarily painful, i hear you. I hear you because i was there when my dad suffered with diabetic nerve pain. If you have diabetes and burning, shooting pain in your feet or hands, dont suffer in silence step on up and ask your doctor about diabetic nerve pain. Tell em cedric sent you. Left at the river. Tarzan know where tarzan go tarzan does not know where tarzan go. Do you know where the waterfall . No, me tarzan, king of jungle. Ask somebody . If youre a couple, you fight over directions. Its what you do. If you want to save on car insurance, you switch to geico. Its what you do. Ohhhhhh do you have to do thattright in my ear . Its how i try to live. How i stay active. So i need nutrition. That wont weigh me down. Without the calories you dont. Try boost 100 calories. Each delicious snack size drink gives you. 25 vitamins and minerals and 10 grams of protein. So its big in nutrition and im not about to swim stay strong. Stay active with boost were back with encouraging medical news in the battle against a growing problem in the u. S. Dangerous peanut allergies in children. New research out today could give new hope to parents of highrisk kids. It found that exposing children early, very early, may help them avoid peanut allergies all together. Nbcs erica hill has details. There you go. Reporter 3yearold cole was born with a high risk for a peanut allergy, but instead of keeping peanuts out of his diet. You like those things . Reporter coles father, an allergist, introduced them when there was no Scientific Evidence one way or the other about how to introduce peanuts to him so i just decided may as well just give it to him. Reporter its the same approach they took with older son calvin now 6. For years the wriz dom was that highrisk children should avoid peanuts, the most prevalent Food Allergen before the age of 2. How about one more . Reporter now research is showing what research showed early on. Theres an 80 reduction in peanut allergies in individual infants and babies that were exposed to peanuts early on in life, so thats very revolutionary. Reporter two new studies published in the new england journal of medicine further support the thinking. The first found most highrisk children who regularly consumed peanuts from the age of four months until age 5 remained allergyfree, even after avoiding peanuts for another year. In a second study, researchers found exposure to other foods at a young age, including eggs, yogurt, sesame and protect against allergies. Very exciting to think that we can have an approach on preventing allergies, particularly food allergies. Were not there yet. Reporter experts recommend consulting with your physician before introducing potential allergens at home. I got green. Reporter the schorer family is confident. Early exposure worked for their boys. Neither has developed a peanut allergy. As a father really made me better that i ended up probably dock the right thing in terms of giving cole and calvin peanuts early. Reporter peace of mind for parents and child. Erica hill, nbc news, up next here tonight, what it takes to get a little snow at one of the worlds what if one piece of kale could protect you from diabetes . What if one situp could prevent Heart Disease . One. Wishful thinking, right . But there is one step you can take to help prevent another serious disease. Pneumococcal pneumonia. If you are 50 or older, one dose of the vaccine can help protect you from an illness that can cause difficulty breathing, and may even put you in the hospital. Even if you have already been vaccinated with another pneumonia vaccine, prevnar 13 may help provide additional protection. Prevnar 13 is used to help prevent infections that cause pneumococcal pneumonia. Prevnar 13 allergic reaction to the vaccine or its ingredients. Immune system, you may have a lower response to the vaccine. Common side effects were pain, redness or swelling at the injection site, limited arm movement, fatigue, headache, muscle or joint pain, less appetite, chills, or rash. Get this one done. Ask your doctor or pharmacist about prevnar 13 today. Whatcha doin . Just prepping for my boss party in a couple weeks. What are those . Crest whitestrips. They whiten way better than paste. Crest 3d white whitestrips. Whiten 25 times better than the leading whitening toothpaste. Id say. Someones making quite an impression. Crest 3d white whitestrips. The way to whiten. Every Auto Insurance policy has a number. But not every Insurance Company the life behind it. Those who have served our nation have earned the very best service in return. Usaa. We know what it means to serve. Get an Auto Insurance quote and see why 92 of our members plan talk, talk, talk, talk, talk, talk, talk, talk, talk, scream. Only one guys done more than talk. Kasich. 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The move follows a disappointing Earnings Report and a big drop in bindingins stock price last month. And in alas cat iditarod sled dog race conjures up images. Frozen north and lots of snow. Not so much this year. They had to ship in tons of the snow for the start of the race. In anchorage since last july 27 inches of snow have fouled in the area compared to even with the special delivery they still had to shorten the track by more than half. When we come back, what 340 days in space morning ted scott ready to hit some balls . Sure. Ooh hey buddy, what s up . This is what it can be like to have shingles. Oh, man. A painful, blistering rash. I keep thinking how did he get this, he s in such good shape. If you had chickenpox, the shingles virus is already inside you. 1 in 3 people will get shingles in their lifetime. Your immune system weakens as you get older and it loses its ability to keep the shingles virus in check. After almost 3 weeks, i just really wanted to give it a shot. The shingles rash can last up to 30 days. You know, i m not feeling it today. Don t worry about it buddy. We ll do it another day. Don t wait until care about develops shingles. Talk to your doctor or pharmacist today about a vaccine that can help prevent shingles. We asked a group of young people when they thought they should start saving for retirement. Then we asked some older people when they actually did start saving. This gap between when we should start saving and when we actually do is one of the reasons why too many of us arent prepared for retirement. Just start as early as you can. Its going to pay off in the future. If we all start saving a little more today, well all be better prepared tomorrow. Prudential. Bring your challenges. politely wait, wait, wait you can t put it in like that. You have to rinse it first. That s baked on alfredo. Bakedon . It s never gonna work. Dish issues . Trust your dishwasher with cascade platinum. It powers. Through. Your toughest stuckon food. Better than finish. Cascade. Fact. Theres an advil specially made for fast relief that goes to work in minutes. The only advil with a rapid for rapid relief of tough pain. Look for advil filmcoated in the white box relief doesnt get any faster than this. He is feeling the weight of the world again, scott kelly set an american record with his 340day mission to the International Space station, but today as tom costello reports kelly admitted his reentry to planet earth has been a little more difficult than he expected. Reporter gang back on the ground for less than 24 hours scott kelly says hes still adjusting to life in one g. Coming back to gravity is harder than leaving gravity. Reporter after a nearly a year in space hes far more fatigued, his muscles much more sore than he was after an earlier fivemonth issue. I also have an issue, you know, my skin because it hadnt touched anything for so long, like any significant contact, its very, very sensitive to almost like a burning feeling wherever i like sit or lie or walk. Reporter doctors say he may also have trouble sleeping at first as he readjusts to a normal daynight his muscles may have bones often become more brittle, and he says he actually grew one and a half inches in space because the spinal column wasnt compressed by gravity, but hes already sclunk back to his normal size. Gravity pushes you back down to side. Reporter a big part of this mission, effects of Long Duration space flight for a future mars mission, comparing scott with his twin brother, former astronaut mark kelly back on earth, both undergoing exhaustive medical exams both in space and on ground and mark kelly today. They have already taken 30 samples of blood. Reporter just 30 tubes. Reporter along his 144 million mile journey his tweets with stunny went viral. Back on earth his first meal was a banana, and after a year without a shower he dreamed of jumping back into his pool in meanwhile, that whole taking some time. Some basketballs yesterday, and i didnt get any of them in the in the net. Reporter settling back in after a year up there. Tom costello, nbc news, houston. That will do it for us on a friday night. Im lester holt. For all of us at nbc news, thank you for watching. Good night and have a good weekend. . head on collision after the third wrong way accident in the past couple of months, a firefighter has an idea to stop it from happening again. so many people would come how a community is using sports to help teens battling cancer. hi russ, are you making plans for the weekend . ill let you know when to expect rain and snow coming up. o. J. simpson back in the spotlight, what could the discovery for a possible discovery of a murder weapon could mean for his future, and whether he can be tried again for the crime. good evening, im russ mitchell, jimmy is off tonight. dramatic video shows the moment a wrong way sedan hit a u haul on the belt. they all survived. reporter it was another wrong way highway crash