Neighborhoods across 15 states fresh out of luck for food. Nightly news begins right now. Announcer this is nbc nightly news with lester holt reporting tonight from washington. Good evening. In a president ial Election Year thats taken some pretty odd directions, add this one to the list. Now five days before the iowa caucus votes republican frontrunner donald trump has abruptly dropped out of tomorrow nights debate in an apparent huff, a decision apparently not rooted in any shrewd political strategy but rather in a spat between trump and fox news which is carrying the debate. For any other candidate, it would be a highly risky move, but as katy tur reports, for this candidate no one is placing bets. Reporter when it comes to donald trump, the only rule is there are no rules. Five days to the caucus and the billionaire is skipping iowa today for south carolina, news debate tomorrow. I dont know what games roger ailes is playing but whats wrong over there. Reporter trump and his Campaign Manager arguing fox isnt fair after it sent out a press release mocking trumps complaints about moderator megyn kelly. The candidate still angry at kelly for reciting things he himself said about women. Unlike the very stupid and highly incompetent people that run our country, mr. Trump knows when to walk away from a reporter trump possibly betting that the risk of a no show is better than the risk of a poor performance. Reporter in response trumps opponents are piling on. Ted cruz not so subtly tweeting that trump is a coward. Reporter the drama making National Headlines but not here in iowa where locals want to get it over with. I dont think hes credible candidate. I wouldnt vote for him if he was the only one running. More drama. More petulant behavior. Reporter even mike deciding between jeb bush and donald trump, says hes heard enough. Wouldnt you want to see another debate to really be able . I dont need it. Reporter okay. I dont need it at this point. If trump is running any risk, its that some voters in iowa may say this is immature, but i think that risk is relatively small, particularly for the people already supporting trump who will look at this not as a petulant move but as a move of strength. Reporter though polling suggests the bigger the turnout the better trump will do caucus night, theres still little sign the campaign has followed through on its get out the vote effort. Late tonight trump announced a counterevent at drake university. Now all of the attention is back on the frontrunner, and, lester, as you know, hes never liked to be challenged. Hes grown increasingly sensitive on the trail lashing out at reporters and now refusing to face a tough moderator. All right, katy, thanks. With democrats Hillary Clinton and Bernie Sanders days away from their showdown in iowa, sanders was here in washington, d. C. , house, where he met with president obama. Its a meeting planned weeks ago. I caught up with senator sanders right after his oval office chat, and he told me their conversation covered domestic and Foreign Policy issues and, yes, politics. It was a private conversation so im not going to get into it but i think if theres anybody in the world who understands what campaigning in iowa and New Hampshire is about and in putting together just an extraordinary Grass Roots Movement that took them to victory, that is barack obama. A few days ago the president speaking to politico seemed to be speaking in glowing terms about secretary clinton, her leadership, her depth of experience. She can start here day one, more nonvice president has to this office. Was tipping his thumb on the scale in her favor. Did you sense that . Nope. I didnt were you bothered by . Nope, i wasnt. And i thought he was very evenhanded. I think there are some people who spun it this way. Bernie sanders whats your bar for success in iowa . Winning. Number one. Yeah. I mean, i think that we have worked really hard. We started off in iowa later than secretary clinton did, but in the last number of months we have put together an incredible volunteer effort. We have 15,000 volunteers, and let me tell be very clear about this, lester. Caucus night in iowa, you will be able to tell very early, i think, who wins and who loses. If there is a large voter turnout, were going to win. If you come in second place, what does that mean for the rest of your campaign . It means that we came in second place in iowa and were off on the run into New Hampshire to try to win there. But is it disappointing . Would be it crushing at the end of the day in terms of delegate selection, if you get 52 or 48 it will mean very few delegates. Psychologically obviously its northern. Word on the street youve got a lot of ad dollars youll be buying on television. Are you going to be going directly at Hillary Clinton . Are you going to turn negative . No, no, no. We differentiate ourselves from secretary clinton every single day. That is what a campaign is about. Lets talk about the significance of your campaign. President obama, the first africanamerican president. Hillary clinton could become the first female president. Not a lot has been talked about the fact that you would become the oldest and the first jewish president. Is that something you reflect on and think about . Sure, i do. Thank god i am in good health and as a former Long Distance runner, was a pretty good miler when i was in high school, did a little running in college, my endurance is strong. In terms of my religion, im very proud of my jewish background, and it has had a significant and one more note from our interview. The New Hampshire union leader is hosting a debate next week that will air on msnbc. Hillary clinton said today that shes in and we asked Bernie Sanders if hes in as well. He said he wasnt ready to commit because he wants to expand on that plan and add additional debates to the schedule as well, so stay tuned there. Want to bring in right now our political director, the moderator of meet the press chuck todd. Chuck, lets go back to donald trump for a moment. Yeah. Is there a hidden strategy perhaps in him refusing to debate and obvious question could it backfire . Well, look, always a chance could backfire. Iowans could be offended by the idea, but heres where it could be a shrewd move. Look, debates havent been Donald Trumps best moments. The most recent debate was probably list best debate but thats grading a little bit on a curve. Hes been fine, not collapsed, but debates only matter to the voters if somebody has a disastrous performance, so heres why it could be a shrewd move. Trump not being there. Wrong thing, but guess what could happen . His chief rival in iowa ted cruz, after five minutes of bashing donald trump for being there, what do you think the rest of the candidates are going to do . Are they going to continue going after donald trump or piling on ted cruz and who benefits more from that, donald trump . This could end up being a very shrewd move by the frontrunner. All right. Chuck, thanks very much. A group of armed antigovernment protesters are still occupying a federal refuge in oregon after their leaders were arrested in a deadly shootout overnight. They seized the refuge over three weeks ago demanding the release of ranchers convicted of setting fires on federal land. As Nbcs Joe Fryer reports, those still at the refuge are strongly being urged to leave. Reporter authorities are tightening their grip around the Malheur National wildlife refuge tonight, blocking roads and setting up checkpoints. Inside the refuge some antigovernment militants remain, not giving up on their armed occupation. Peaceful resolution is what you keep resolution is what we expect. Reporter many of the greens leaders, including ammon bundy are now occupying a jail cell. While driving along a rural highway yesterday, some were stopped by the fbi and state police. The senior Law Enforcement official tells nbc news one vehicle drove off and hit a snow bank and then Lavoy Finicum emerged brandishing a firearm. He was shot and killed. Im disappointed that a traffic stop yesterday that was supposed to bring peaceful resolution to this ended badly. Reporter three weeks ago, finicum said hed rather die than go to jail. I have no intention of spending any of my days in a concrete box. Reporter but his daughter says he would never put someones life in jeopardy. Hes a great man and just because he said he doesnt mean that his night wont go on. Hes now had a martyr. Reporter during the highway confrontation another militant ryan bundy was shot in the arm today seven suspects including the bundy brothers appeared in federal court facing felony charges. Another occupier John Ritzheimer was arrested in arizona. He had just returned home to see his family. Three and a half weeks have passed since the armed group took control of the wildlife refuge. Now the fbi says those remaining need to pack up and go and wont be arrested. If the people on the refuge want to leave, they are free to do so. Reporter a lit development tonight. Ammon bundy through his attorney is asking the remaining occupiers to stand down and go home. Its unclear how many militants remain at the refuge, but we know after the events that happened yesterday some did pack up and leave earlier today. Lester . All right, joe, thanks. In south florida today, wild scenes as a tornado rolled through new ft. Lauderdale with winds near 100 Miles Per Hour flipping cars on a college campus, damaging roofs and leaving hundreds of homes without power. At least one person was injured. Warning tonight from doctors. American doctors that the zika virus is a pandemic demanding a more aggressive Global Response and Top Public Health experts are saying the u. S. Must do more to prepare for zika as American Airlines expands refunds offered to pregnant women who booked flights to affected countries. Nbcs tom costello has the new details. Reporter in the streets of rio, celebration before carnivale expected to draw more than a million turnists, but the conditions here are perfect for mosquitos, hot and muggy with lots of standing water. Nbc news was with sanitation crews dispatched to wipe out zikacarrying mosquitos already linked to 4,000 cases of microcephaly in brazil, babies born with deformed heads and brains. 24 countries and territories are now on the cdcs list of areas that pregnant women or women who could become pregnant should avoid. Meanwhile in a top medical journal today, two top american researchers accused organization of failing to act fast enough. Now we have a pandemic. It started to involve multiple continents, and certainly many countries, more than 21 countries in the americas. We need Global Leadership for this evolving rapidly accelerating health problem. Reporter while travelers infected with zika abroad have already returned to the u. S. , there is growing concern that zika mosquitos could soon spread to the southern u. S. States and then spread north with warmer weather. Become in brazil with carnivale and olympic tourists expected this summer, a quarter of a million soldiers are now on Mosquito Control missions and carolina lobo is seven months pregnant. Im worried because i cant have a baby with microcephaly and i dont want it, nobody wants it. Reporter president obama is pushing american researchers to develop a vaccine quickly, but that could be years away. The good news. People who arent pregnant and contract mild symptoms if any at all and then have immunity for life. Tom costello, nbc news, washington. A Grade School Principal from indiana is being hailed as a hero for saving her students from a horrific bus crash, but sadly as nbcs blake mccoy tells us, she gave her life to protect those children. Reporter parents and kids in mourning over the death of their beloved Elementary School principal, 69yearold susan jordan killed in a freak accident tuesday when a school bus unexpectedly lurched forward, jumping the curb. In her final moments witnesses say jordan pushed children out of harms way. We started Going Forward and we hit a tree and i was just really scared because i didnt know what was going to happen. Reporter two 10yearolds were injured in the accident but are expected to be okay. Boys and girls, this is National Kindness week. Reporter jordan had been principal of amy beveland elementary for 22 years, someone who whether it was making pancakes or handing out birthday cards to each student. When you heard that in her final moments she was pushing kids out of the way to save them from that bus. I said thats our susan. Thats our susan. Shes a hero. She was had a hero every day. Reporter what caused the bus to suddenly jolt forward is under investigation. The School District says the driver showed no signs of being under the influence of drugs or alcohol. Tests are being done. And were told that this bus had just passed regular inspection last friday. There were no violations found that contributed to the crash. Reporter classes resume tomorrow, and while the building will be open, its heart and soul will be missing. Blake mccoy, nbc news, indianapolis, indiana. Weve got more to tell you about here tonight. Still ahead, shock waves across america as the Worlds Largest retailer prepares to close many of its stores. We take you to one community thats losing much more than also, why super bowlbound quarterback Peyton Manning is facing an nfl music woman i ll never remember all the projects, presentations, my nights for. music s drums intensify i ll never forget. In the 2016 ford escape. Be unstoppable. This is my fight song take back my life song music this is sheldon whose long day setting up the news starts with minor arthritis pain and a choice. Take tylenol or take aleve, the 1 recommended pain reliever by orthopedic doctors. Just two aleve can keep pain away all day. 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 prevnar 13 vaccine can help protect you from pneumococcal pneumonia, an illness that can cause coughing, chest pain, 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 in adults 50 and older to help prevent infections from 13 strains of the bacteria that cause 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, fatigue, headache, muscle or joint pain, less appetite, chills, or rash. Ask your doctor or pharmacist about prevnar 13 today. By tomorrow walmart will have shut down almost all of the 154 stores that it has targeted for closure around the nation. All of its express locations are closing, many of which are in small towns. Nbcs Gabe Gutierrez takes us to one of the many communities that will struggle to find fresh food after reporter in tiny oriental, north carolina, population 900, everything changed when the giant came to town. It was bad. I mean, immediately it affected us. Can tills peter mehegan. Reporter for 44 years renee smiths family ran a Grocery Store here and then a walmart express came along and 17 months later she closed her doors. And i feel it was very malicious of them to leave this town in the shape that its it. Reporter now walmart is closing more than 150 stores in the u. S. , turning oriental into a food desert without a single Grocery Store. Anybody here that wants to buy an onion now has to drive about a 40mile round trip. Reporter this location in california is set to close tomorrow. Around the country many communities are worried about what this will mean for their economies. Walmarts ceo points out the Company Plans to open 300 new locations around the world. An easy decision, he says, but it is necessary to keep the Company Strong and positioned for the future. They werent really in the right location and the product mix just wasnt right. Reporter Rebecca Anderson was laid off when walmart opened near the mom and pop store where she worked. Its just all about the people and they were all about us and when walmart came, it was no more. Reporter tonight she and so many others are wondering what will fill the void now that the giant is leaving town . Gabe gutierrez, nbc news, altadena, california. 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