happen to you. and hidden risk. when even exercise won't lower the cholesterol. what doctors say you need to get rid of to bring it down. "nightly news" begins right now. from nbc news world headquarters in nightly news" with lester holt. good evening. it's virtually unheard of, a pope admonishing a u.s. presidential candidate, in this case [ bleep ] donald trump over his immigration plan. pope francis returning home took the reporter's question about trump's pledge to build a border wall. in his answer, implied that trump is not a christian. it was a high-level rebuke to say the least. but true to form, trump is not turning the other cheek. nbc's katy tur has the details. >> mr. trump, the pope made a statement about you. trump proving there is no thing or one too sacred for his political ire. >> he actually said i'm not a good christian or something. >> reporter: the last presbyterian lashing out at the church. talking about the border wall between the u.s. and mexico. a person who only thinks about building walls wherever they may be, and not building bridges is not a christian, he told reporters. just hours earlier, the pontiff was praying along the mexican side of that very border. donald trump declared his holiness should hope it's him. >> if and when the vatican is attacked by isis, which as everyone knows is isis' ultimate trophy, i can promise you that the pope would have only wished and prayed that donald trump would have been president. >> reporter: another day, another controversy, but still no clear break in his support. >> i think he has to respond. him. >> donald trump is a good christian, as is >> reporter: south carolina is known for its religious voting block, but only 13% of republican primary voters in 2012 were nationally that number jumps to 25%. swing voters who three presidents. >> it's not unusual at owl for pope francis to talk about the dignity of the president. >> reporter: trump even admonished the holy father for something trump himself did to ted cruz last week, questioning his faith. >> for a religious leader to question someone's faith is disgraceful. >> reporter: the top trend right now on twitter, this feud between donald trump and the pope. the pope himself does live behind very high walls that surround the vatican. lester. >> katy tur tonight, thank you. it's getting uglier on the campaign trail in south carolina with cruz and rubio trading accusations of dirty from a critical primary. nbc's dave gutierrez frames the dispute for us. >> reporter: if a picture's worth a thousand words, today the bitter fight between ted cruz and marco rubio got expensive. >> making things up, they literally made up a picture. >> reporter: rubio claiming the florida senator shook hands with president obama, and supported amnesty for undocumented immigrants. the cruz campaign firing back. it's just pointing out rubio shifting stance on immigration. the texas senator also trying to build momentum in his battle against donald trump. >> in the "wall street journal," and for the first time in many, many months, according to that poll, there's a new national front-runner. >> reporter: rubio's getting a jolt from the surprise endorsement of governor nikki haley who had been heavily courted by the bush she has an 81% approval rating among republican voters here. >> jeb is a dear friend. this is about fight, this is about passion. >> reporter: bush tried to convince voters that his fight isn't over. for rubio, saturday could be crucial. tonight a diverse trio is on the trail. a cuban-american presidential candidate, an indian-american governor and african-american senator. >> are you the new face of the republican party? >> are we the new republican party? i hope we're the faces of the new conservative movement. >> reporter: an emotional supporter at a john kasich rally. what you've been talking about. [ cheers and applause ] >> reporter: he got the hug after sharing a difficult story about the tough period in his life over the past year. he says he sees hope in john kasich's tomorrow will be a south carolina. gop candidates planning at least 20 stops throughout the lester? >> dave gutierrez tonight, thank you. democrats are preparing for a critical showdown at the msnbc town hall in las vegas. where the polls are showing it's a dead heat ahead of the nevada caucuses. clinton has a smaller lead before sanders' blowout victory in new hampshire. andrea mitchell has the details on a tightening contest. >> reporter: hillary clinton today reaching out to casino workers after seeing her support in nevada plummet over the last two weeks. >> thank you so much. >> reporter: both democrats now targeting minorities in the diverse state. bernie sanders meeting today with the urban league in washington. competing with clinton to champion their history. >> the fight for basic voting rights, the demonstrations, the beatings, african-americans need to achieve what all americans have, the right to vote. >> reporter: both latinos. today clinton rolling out a new ad featuring a 10-year-old girl who fears her parents will be deported. >> let me do the worrying. i'll do all the is that a deal? i'll do everything i can to help. >> reporter: president obama is granting exceptions to undocumented teenagers and young adults. so-called dreamers. but not their parents. a huge issue here. sanders supporter is 18. citizens. we want everything that citizens get in the united states. we just want to feel like we're home. supporter perez came from the philippines when she was 6. >> we need to tell the gop, we need to tell the democrats, hey, you know what, we're out here and what are you going to do? you can't deport all 11 million, 12 million of us. >> i think what they really fear, andrea, is all kinds of new voters that bernie sanders is atacting connelling out to vote and skewing the results. >> reporter: don't joe biden who didn't run tells rachel maddow -- >> i don't regret it. it's the right decision for my family, and me. >> reporter: leading attacks against bernie sanders, speaking tonight at the same democratic party dinner as sanders. even as sanders and hillary clinton will be answering questions at that msnbc town hall here. lester? >> andrea, thank you. you can see the clinton and sanders town hall tonight at 9:00 eastern only on msnbc. a historic announcement from the white house today. president obama will become the first sitting president to visit cuba in nearly 90 years. a major step as the u.s. and cuba move to normalize relations. the trip which is planned for march 21st and 22nd was immediately met with criticism from republicans, including ted cruz, who said he would never visit as long as castro is in power. there was something else pope besides his comments on donald trump, that took many by surprise. he suggested birth control may be used to prevent the spread of the zika virus, which has been linked to birth defects. this despite the catholic church's ban on contraceptives, we get more from nbc's anne thompson in rome. >> reporter: returning from mexico, pope francis surprised many by opening the door to the use of artificial contraception to prevent the sexual transmission of zika, the vi rugs rampant in his native latin america, linked to babies born with unusually small heads. it's similar, he said, granted to the nuns in the belgian congo when they were routinely raped in the 1960s. francis continues to shock, as he did in 2013 when he said the church has been historically too obsessed with things like birth control, >> to say he's simply loosening up church teaching is a misreading of what he's doing. this is a pastor, and a pastor responds to situation. >> reporter: it was revealed in letters this week, francis said a friendship with a woman is not a sin. input of women. he said a man who doesn't have a friendship with a woman is missing something. as with donald trump and immigration, pope francis is proving once again that he is not afraid of taking on controversial topics, trying to resolve issues of faith with real-world problems. lester. >> anne thompson outside the vatican tonight, thanks. apple is getting some backup from some fellow tech companies today tas battles an fbi request to unlock an iphone used by one of the san bernardino terrorists. as nbc's pete williams reports, apple's resistance proving highly controversial. >> reporter: the battle is waging investigation. the fbi searching the homes of two relatives of san bernardino gunman farouk. the ceo of google is now backing apple. requiring companies to enable hacking of customer devices and data, he says, could be a troubling precedent. other tech giants, including microsoft, facebook and twitter added their support. so did apple's co-founder, steve wozniak, on cnbc. >> i think you should feel this is my product and what i have is what i think i have. i don't have companies playing tricks behind me in the background. >> reporter: but police are pushing back. prosecutors in new york say they have 175 apple devices they cannot open for evidence, in crimes ranging from identity theft to murder. >> this has become, ladies and gentlemen, the wild west in technology. apple and google are their over sheriffs. there are no rules. >> reporter: and mandy, whose fiance was killed in san bernardino, says this presents a tough choice. >> i would love to get possible of shannon's murder, and the other 13 people who were killed. but i'm also an american. i like my privacy. >> reporter: business experts say the battle is about marketing, because protecting privacy is key to apple's image. >> the people need to feel that what they're buying is theirs, and is truly empowering. that's what the apple brand is built upon. >> reporter: apple says tonight the government doesn't have the legal authority to make it create new software, and help the fbi open a locked phone. no federal court has ever ruled on that. pete williams, nbc news, washington. a hostage and ransom story for the digital age. a medical center in california forced to pay cyber criminals thousands of dollars to gain back control of its computers. it's a trend called ransomware. hackers infecting computers with malware, then demanding ransom to give it back. it could happen to you. >> reporter: it happened at hollywood center. hackers demanding $17,000 in ransom payable in online bit coins to release the computers. locked out, the hospital's ceo says in the best interests of restoring normal operations, we did this. across the country in maine, hackers even held the lincoln county sheriff's computers hostage. >> they asked for, we'll gladly give you a code to unencrypt it for a fee. >> reporter: they paid $300 to get their data back. >> they've already encrypted most of the information on your system. >> reporter: cybersecurity james said ransomware is now big business. encrypting corporate and government files, family photo, health records and financial documents, then demanding payment for the code to unlock them. becoming a victim is as easy as a bad mouse click on a pop-up window, e-mail or web link. this would be the data on my computer. i can't access it anymore. whether they're photos, excel files. these guys are playing. that's the business model they're using right now. pros recommend updating your anti-virus software, enabling your pop-up blockers, and backing up your computer on an external drive. with the hackers often a world away, if you have no choice but to pay the ransom. tom costello, nbc news, washington. staying in california for a moment, an update on a major environmental drama we have been covering, the leak from a ruptured well that has been spewing massive amounts of natural gas into the air near los angeles, has been permanently sealed. state officials said it comes after four months of making people sick and forcing thousands of families from their homes in porter ranch. southern california gas is facing multiple lawsuits and investigations. there's a lot more tonight. lowering your cholesterol. the often overlooked factor that experts say could make all the difference, even when statins, dieting and exercise aren't effective enough. also, caught on camera, a tour chopper plunging into pearl song: "that's life" song: "that's life" song: "that's life" p song: "that'splife" that's life. you diet. you exercise. and if you still need help lowering your blood sugar... ...this is jardiance. along with diet and exercise, jardiance works around the clock to lower blood sugar in adults with type 2 diabetes. it works by helping your body to get rid of some of the sugar it doesn't need through urination. this can help you lower blood sugar and a1c. and although it's not for weight loss or lowering systolic jardiance could help with both. jardiance can cause serious side effects 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recommend focusing on one of the most significant cholesterol factors is one of the most overlooked. lowering stress can have a major impact. >> reporter: college professor christopher edging was going nonstop, classes, meetings and consulting. >> i was wearing four different hats. and working about 60 to 70 hours a week and really not getting very much sleep at all. >> reporter: the university of northern iowa professor was around the world. in one month alone, to south korea, germany, hong kong and canada. >> i could just see that he was going a hundred miles an hour with multiple secretaries delegating things. >> reporter: then a wakeup call, two heart attacks. even though he changed his diet and took statins, his cholesterol kept rising. that's when his mayo clinic doctor suggested using an overlooked risk realize how important that is. >> reporter: experts say stress can release hormones that increase fat cells, which can boost the bad type of cholesterol known as ldl. >> i don't want to discourage people from taking pills. it's also important to look at the other half of the equation, which is diet, exercise and stress. >> when you come back to the united states -- >> reporter: when edgington cut back on his work and started spending more time with his grandchildren, a dramatic change. his cholesterol fell by nearly half, from 121 to 62. >> i tell my students, find one hour every day to take care of yourself. do something, whether it's physical, mental, or whatever. >> reporter: he's following his doctor's advice, ending each day, thinking of three things for which he's grateful. tonic for a stress-filled life. janet shamlian, nbc news, houston. we're back in a moment with the perfect conditions creating a rare fiery if you're looking to save medicare part d prescriptions, walgreens says, carpe med diem. seize the day to get more out of life and medicare part d. just switch to walgreens for savings that'll be the highlight of your day. now preview the cost of 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near the "uss arizona" memorial at pearl harbor, with five people onboard. it was then that almaguer explains onlookers sprang into action. >> reporter: witnesses could tell something was wrong. the tail of the sight-seeing helicopter was smoking as it quickly descended toward the rocky shoreline. then the moment of impact. with the chopper sinking, several good samaritans plunged into the water to rescue the trapped passengers. >> i saw the helicopter sputtering about 500 feet. the pilot did an amaze amazing job. >> reporter: five people were pulled ashore. at least one suffering critical injuries. all rushed to hospitals by ambulance. the navy says the helicopter is owned by genesis aviation. the same chopper seen here before the crash. of the arizona memorial since 1999. tonight the investigation into what went wrong is under way. witnesses say it's a miracle everyone survived. miguel almaguer, nbc news. now to a rare and amazing sight in yosemite national park. what's known as a 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pneumococcal pneumonia. you should not receive prevnar 13 if you have had a severe allergic reaction to the vaccine or its ingredients. if you have a weakened 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, less appetite, chills, or rash. get this one done. ask your doctor or pharmacist about prevnar 13 today. finally tonight, remember the days when we had photo albums on our shelves? not just on our phones? the digital era has largely sent photo prints the way of the walkman, and kids, we'll explain that another time. but as joe fryer said they're making a comeback, even in this age of instant gratification. >> reporter: for a while it seemed our photos were not hanging on real walls, but facebook walls. now a las vegas business is bringing those images back to >> i thought it might be a way to get pictures off of my dadgum iphone. >> reporter: instant photography is having a renaissance. not only do they sell the refurbished polaroids and other instant cameras, but they can actually print their pics. >> what if we could create this experienceial photo. >> reporter: step one, take a picture. from there, just send it to one of the company's computers. >> reporter: and within minutes, you've got a picture on paper. of course, instant photography is nothing new. for decades, polaroids were a pop culture phenomenon. but as the focus shifted to digital cameras, the company had to declare bankruptcy, twice. >> this is the polaroid is back with new products and new customers. millennials. >> to them, instant photography is magical, something they did not grow up with. >> reporter: for the under 30 crowd, real-life photos are trending. >> we've had kids, millennials come into the store and for the first time ever in their lives hold a physical photo in their hands. it's incredible. >> reporter: proof an image doesn't have to go viral to be memorable. joe fryer, nbc news, las vegas. that's going to do it for us on a