In a president ial Election Year that has 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 purportedly 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, with this candidate, no one is placing bets. Reporter when it comes to donald trump, the only rule is there are no rules. Five days before the caucus and the billionaire is skipping iowa today for south carolina. And skipping the fox news debate tomorrow. I was not treated well by fox. They came out with this ridiculous statement. It was like it was drawn up by a child. It was a taunt. I said, how much of this do you take. Reporter they say it sent out a press release about megyn kelly. The candidate still angry at kelly about what he said about women. Unlike the very stupid and highly incompetent people that run our country, mr. Trump knows when to walk away from a bad deal. Reporter he said the noshow is better than the risk of a poor performance. In response, trumps opponents are piling on. Ted cruz not so subtly tweeting trump is a coward. The drama making national headlines. But not here in iowa. Where locals want to get it over with. I dont think hes credible. I wouldnt vote for him if he was the only one running. More drama. More pet you lent behavior. Reporter beecher was Still Deciding between jeb bush and donald trump, said hes heard enough. Wouldnt you want to see another debate to really i dont need it. I dont need it at this point. If trumps running 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 not see this as a petulant move. Reporter 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 counter event at drake university. Now all of the attention is back on the frontrunner. Lester, as you know, challenged. Increasingly sensitive on this. Lashing out at reporters and now refusing to face a tough moderator. With democrats, Hillary Clinton and Bernie Sanders days away from their showdown in iowa. Sanders was here in washington, d. C. , specifically the white house, where he met with president obama. 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 and, yes, politics. It was a private conversation, so im not going to get into it. I think if theres anybody in the world who understands what campaigning in iowa, in New Hampshire is about, and putting together just an extraordinary Grass Roots Movement that took him 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 experienced than any nonvice president has ever been. Who aspires to this office. Some people say he was tipping his thumb on the scale in her do you sense that . No. It . No, i wasnt. I read the interview, and i thought he was very evenhanded. Some people who spun it that way. Winning. Number one. Yeah. I mean, i think that we have worked really hard. We started off in iowa later than secretary clinton did. In the last number of months, we have put together an incredible volunteer effort. We have 15,000 volunteers. Let me be very clear about this. Caucus night in iowa, you will be able to tell very early 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. Were off and running to New Hampshire to win there. Would it be crushing . Would it get you off your game . In terms of delegate election, you get 52 or 48 . It will mean very few delegates. Psychologically, obviously, its important. The word on the street youve got a youre buying on television. Are you going to be going directly at Hillary Clinton . Are you going to turn negative . No. No. We differentiate ourselves from secretary clinton every day. Lets talk about the significance of your campaign. President obama, the first africanamerican president , and Hillary Clinton could become the first female president. Not a lot of talk about you being the oldest and first jewish president. Is that something you think about . Sure i do. Thank god i am in good health. And as a former longdistance runner, 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 influence on me. 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 shes in, and we asked Bernie Sanders if hes he said he wasnt ready to commit because he wants to expand on that plan. I want to bring in our political director, the moderator of meet the press, chuck todd. Chuck, lets go back to donald trump for a moment. Is there a hidden strategy perhaps in him refusing to debate . And could it backfire . Theres always a chance it could backfire. Iowans could be offended by the idea. Heres where it could be a shrewd move. Debates havent been Donald Trumps best moments. The most recent is probably his best debate. But thats grading on a curve. Debates only matter to the voters if somebody has a disastrous performance. Heres why it could be a shrewd move. Trump not being there, theres no way he could make a mistake and say the wrong thing. But 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 continue to go after donald trump or go after ted cruz . This could end up being a very shrewd move by the front runner. Todd, thank you very much. The armed antigovernment protesters are still occupying a federal refuge. They seized the refuge over three weeks ago demanding the release of ranchers convicted of setting fires on federal land. As joe frye reports, those at the refuge are being strongly urged to leave. Reporter authorities are tightening their grip around the 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 we expect. Reporter many of the leaders are now occupying a jail cell. While driving along a rural highway yesterday, some were stopped by the fbi and state police. Official tells nbc news one vehicle drove off and hit a snow bank, then one emerged brandishing a firearm and was shot and killed. Disappointing yesterday. It was supposed to bring peaceful resolution to this. Ended badly. Reporter three weeks ago he said he go to jail. I have no intention of spending any of my box. Reporter his daughter said he would never put someones life in jeopardy. Hes a great man. And just because what he said doesnt mean that his fight wont go on. Hes now a martyr. Reporter during the highway confrontation, another militant, ryan bundy, was shot in the arm but survived. Seven suspects, including the bundy brothers, appeared in federal court facing felony charges. Another occupier was arrested in arizona. He had just returned 3 1 2 weeks have passed since the armed group took control of the wildlife refuge. Now the fbi said those remaining need to pack up and go and wont be arrested. If the people on the refuge want to leave, theyre free to do so. Reporter a Late Development tonight. Bundy 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 near ft. Lauderdale with winds there 100 miles an hour, flipping cars on a college campus, damaging roofs, and leaving hundreds of homes without power. At least one person was injured. Theres a new warning tonight from doctors. American doctors at that the ziko virus is a pandemic. Top Public Health u. S. Must do more to prepare for zika. Tom costello has the new details. Reporter in the streets of rio, celebration before carnivale, expected to draw more than 1 million tourists. But the conditions here are perfect for mosquitoes, hot and muggy with lots of standing water. Nbc news was with sanitation crews dispatched to wipe out zikacarrying mosquitoes, already linked to cases of babies born with deformed heads and brains. Its one of the areas where pregnant women or women who could become pregnant should avoid. Two top american researchers accused the World Health Organization of failing to act fast enough. Now we have a pandemic. It started to involve multiple continents, and certainly many countries, more than 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 mosquitoes could soon spread to the southern united states, and then spread to warmer weather. Tourists expected this summer, a quarter of a million soldiers are now on Mosquito Control missions. Carlina is seven months pregnant. I can have a baby with 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 zika should develop only mild symptoms, if any at all, and then have immunity for life. A Grade School Principal from indiana is being hailed as a hero for saving her horrific bus crash. Sadly, as blake mccoy tells us, she gave her life to protect those children. Reporter parents and kids in mourning over the death of their beloved principal. She was killed in a freak accident tuesday when a school bus unexpectedly lurched forward jumping the curve. In her final moments, witnesses say jordan pushed children out of the 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 for 22 years. Someone who always put kids first, 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 susan. Thats our susan. Shes a hero. She was 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. 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 big discounts. Also, why super bowlbound quarterback Peyton Manning is investigation. By tomorrow, walmart will have shut down almost all of the 150 stores it has targeted foreclosure around the nation. All of its express locations are closing, many of which are in small towns. Gabe gutierrez takes us to one of the many communities who will struggle to find fresh food after walmart leaves. Reporter in tiny oriental, north carolina, population 900. Everything changed when the giant came into town. It was fast. Immediately. It kills me. Reporter for 44 years, rene smiths family ran a Grocery Store here. Then a walmart express came along. 17 months later she closed her doors. It was malicious of them to leave this town in the shape its in. Reporter now walmarts 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 economy. Walmart claims to open 300 new locations around the world. Closing stores is never an easy decision, he said. But it is necessary to keep the Company Strong for the future. They really werent in the right locations. The product mix just Rebecca Anderson was laid off when they opened near the mom and pop store. They were all about us. When walmart came, it was no more. Reporter the night she and so many others are wondering, what will fill the void now that the giant is leaving town. Gabe gutierrez, nbc news, california. When ke come back here tonight, many complained that plows werent out in force after the blizzard of 2016. Parking police were. A potential cloud hanging over the super bowl. The nfl says it is conducting a comprehensive review of allegations in a report by al jazeera that broncos quarterback Peyton Manning had human growth hormones shipped to his home. The league says it will not have results before the big game. Manning has denied using performanceenhancing substances. Here in washington, d. C. , hit with a huge tab after the blizzard of 2016 shut the city down. The district which struggled mightily to clear the streets of snow turned out to be pretty efficient when it came to handing out more than 1 million in parking tickets. More than 65,000 in fines since the storm hit on friday. More than 600 cars were towed. This evening the snow emergency here has finally expired. You think 1 million is cool . How about 5. 8 billion. Thats how much facebook gained in revenue in the last three months of 2015. Rapid growth as the social networking giant seeks to challenge google as the most powerful internet behemoth. When we come back, what michigans governor said about flints water crisis aired last night. Just a day after we reported that none of the lead pipes poisoning the water in flint, michigan, are being removed, rick snider said there are no plans to replace all of them. Instead, theyre relying on water treatments to build up a protective coating inside the pipes. In the meantime, the community continues to suffer. We asked our Kevin Tibbles to visit flint and talk to the impact on their lives about our series we the people. Reporter mcintosh used to be straight up middle class. But no more. For many that dream has died in flint. The loss of industry, the loss of jobs, and now their water is tainted with lead. Along mcintosh drive, anger. My normal life has totally changed. No more life like it used to be. Thats gone. Reporter shes lived here nearly 20 years. She wants to move but says now the house will never sell. They failed to tell the truth. I cant get past that. How could you give somebody poise on . Reporter strong questions for her government, which many in flint feel have abandoned them. Across the street, the hodges. Father shane has three kids under the age of 6. The effect of lead on a childs the fear of unknowing. Reporter in this home they await the results of lead testing. At night i pray, i pray on my knees that everything will be taken care of. Reporter neighbor rodney has lost faith. Somebodys got to be accountable. Thats the way i look at it. Reporter in a city of almost 100,000 where more than 40 live below the poverty line, they are stunned by the indifference. We do not count. Theyve lied to us, and theyve left us behind. Whatever happens to us doesnt matter. Reporter left behind, on mcintosh drive, and facing an uncertain future again. Kevin tibbles, nbc news, flint. A program note. Tonight my colleague Rachel Maddow will hold a town hall on this. For all of us at nbc news, thanks for