First well go to Major Garrett with the republicans tonight. Major . Reporter scott, to win donald trump needs massive new turnout,t,housands of voters participating statewide. Four years ago turnout was about 122,000. Ted cruz is betting everything here, his Massive Organization can withstand vwter turnout up to 170,000, but beyond that, it is trumps game and trumps night. Good morning. Its the day weve been waiting for. Reporter before dawn, ken brolininoke up 130 ted cruz central central tears living in this apartment complexes known as camp cruz. We give this our all for one moredy and wean be proud of what we did here. He is real. Reporter cruz volunteers worked the phones all day sunday at the Campaign Headquarters outside des moines, part of the largest mobile disition effort of any g. O. P. Candidate. Cruz himselfs in his 99th and final iowa county today and i got to tell you, this race right now is neck and neck. Its all about turno. Reporter Donald Trump Holding a small but significant lead on cruz said he was nervous facing voters for the first time. Win, lose or draw, i love you lks all. I love you all. Reporter trump also warned iowa corn farmers who rely on federal ethanol subsidies that cruz is no friend. He will destroy your ethanol business 100 , 100 . Thanks for everything. Reporter marcocoubio who is hoping a late surge will translater to a strong finish exhorted volunteers and took selfies. Were ready forhatever happens tonight. We feel positive about it. I ask everyone to go ououand caucus, especiallylyf youre supporting me. Were volunteers of ben carsons campaign. Reporter supporters of ben carson who has sagged in the polls knocked on doors in one last gasp of s sport. And rand paul met with dozens of his young volunteers. Were going to do very well. Were going to beat a lot of people in the race. Win. Reporter rubio could be the one to watch, scott. His crowds have grown by hundreds down the stretch, and a strong finish could be a spring board to New Hampshire, where other rivals for the socalled republican estababshment vote, jeb bush, Chris Christie and general kasich, are already waiting. Pelley major, thanks. Now the last precaucus poll out today shows the democratic race between clinton and sanders a statattical dead heat. Clinton hopes to redeem her loss in iowa eight years ago. Nancy cordes is there. Nancy . Reporter scott, clinton came into iowa with all the advantages must be, stats, years of planning. Tonight we find out if it is enough to fend off a former underdog who, like her opponent eight years ago, has taken on an iowa with a message about change. I really appreciate all your help. Reporter there was nothing left to do today but thank supporters. Let me thank not only all the volunteers. Would you be able to come . Reporter the doors have all been knocked on. I will be caucusing tomorrow. For bernie . Bernie, yes. Excellent. Reporter and no one has any idea who will come out on top. We got a tie ballgame. Reporter vermont senator Bernie Sanders has closed a 40point gap in six months. The adrenaline is flowing, yes. Reporter win or lose, he has pierced clintons aura of inevitability. What was the point that you thought, i could really be a contender here . Well, when we started to bring out really, really large turnouts, you know, in des moines and iowa city and people said, you know, bernie, for iowa thats a really, really big turnout. Reporter clinton, by necessity or design, has done smaller events. How many people here have already made a phone call or knocked on a door . Reporter making more time for the kind of personal interaction iowans see as a birth right. The candidates closing stick with me. Stick with the plan. Stick with experience. It sounds like you want to make a political revolution. Reporter their faceoff has left former Maryland GovernorMartin Omalley a distant third. If you dont change the dynamic here, what happens in New Hampshire . We. Look, you have to ask me that after monday night. Reporter clinton could survive a loss here in iowa, but it wouldnt be much fun. Sanders is leaving in his neighboring state of New Hampshire by as much as 20 points in the polls, and if he win, scott, clinton wont have chance to redeem herself until South Carolina at the end of the month. Pelley nancy, thank you. Its worth remembering that only 30 delegates are at stake the tonight. It takes many hundreds to win either partys nomination. John dickerson is our cbs news political director and anchor of face the nation. Hes in iowa talking to iowans. John, iowas conservatives are about as conservative as they tailormade for cruz. What if he comes in second . It would be a blow. His campaign is always predicated on starting and doing well in iowa. That is because its tailormade for him there. There are so m my evangelical voters here and conservative voters. His entire campaign is built around this idea that he can build a conservative revolution. If he cant do that here, it calls the whole thing enter question. But he has about 20 million cash on hand, and there are future contests in South Carolina and then a number of Southern States on first of march that would do well for him, so if he comes in second here, he could mount a comeback in those states. Pelley it also seems that iowas liberals are tailormade for sanders. Hell do well in New Hampshire next to his home state next week, but what about the later primaries for sanders . Reporter those laters primaries, the lech track is less liberal. Hillary clinton has Better Organization in those states, so its harder for sanders to build the kind of emotional support and wave that hes trying to build here in iowa. Thats why iowa is so important. Hes not going to be able to do it in later states. Pelley major was just telling us mainstream republicans are fighting for third place. Why does that matter . Reporter well, those mainstream republicans, and here were talking about rubio, bush, christie, kasich, theyve beeee trying the find some reason to break out of the pack and say i am the lone alternative to donald trump and ted cruz. So theyve grabbed a poll. Performance. Broke out of the pack. If they can point to a strong result in iowa, third or maybe second, they can say the voters have validated me and now all mainstream conservatives should rally around me to go up against trump and cruz. Pelley john dickerson, see you on face the nation, thanks, john. Now, we are thrilled to welcome back to the evening news man who has covered every president ial election since 1968, o o very own bob schieffer. Bob, how does this one look to you . Reporter thank you, scott. I have to say, primary campaigns are like weddings, they bring if this campaign were a wedding, we would be halfway through the weird uncles long, unfunny and embarrassing rehearsal dinner toast. The difference here is all the participants in thihi campaign appear to be stonecold sober. That may be the scariest part of all. People are madder than ever, the partisan divide is wider than ever, and were seeing a campaign reflectctg the changes in our culture brought on by social media. Nasty, illogical, illtempered, strong on attitude, light on issues. Too many times people have arrived at this wedding with not just opinions, but their own set of facts. The Campaign Narrative has gone in inane to profane, more like a thread on a blog post than t t usual campaign rhetoric. Youre a jerk. Well, youre a bigger jerk. No, youre a blank, blank jerk. Inspirational . Not just yet. But there is light at the end of e church. In iowa tonight, as the long walk down the aisle of the caucus and primaries, well finally start the hear from another group voters. Scott, thats a good thing. Drew . Pelley and youll be with us on the long walk to ewill election day. Bob, thank you. We will have updates for you tonight on the caucuses during prime time programming. Stick with us right here on cbs. And cbs thursday cbs this morning will have the l lest tomorrow. Snow is on the way tonight in iowa, but not until after the caucuses. California got hammered by weather the past two days, and san diego and eightfootwide oak fell on a cararnd killed a woman. Wind gusts were reported as high as 115mph. To the north i80 was shut after a pileup of 29 vehicles. This system could dump a foot of snow on denver. Took the rare step today of declaring zika virus and its suspectetelink to severee birth defects and International Public health emergency. The outbreak started in brazil and our doctor jon lapook is there tonight. Jon . Reporter scott, i spent the day at this hospital, which has seen the most number of brazil. The couple i spoke to was anguished as they tried to figure out what this condition means for their baby. Alice Bezerra Depaz had a healthy first baby, but two months ago her second child, joao heitor, was born with microcephaly, a birth defect linked to the zika outbreak. Babies with microcephaly have an unusually small head and developmental delays. Infant like this, she saiai bb we will care for him the same way. Today the parents came to the oswaldo cruz hospital where doctors have seen about 300 infants with microcephaly since septememr. Before that this region only saw an average of nine cases a year. Dr. Angela rocha heads up the effort here to understand and manage thehe crisis. In her four decades as a pediatric Infectious Diseases expert, she has never seen anything like it. This is different, she said. Its s generation of b bies with disabilities, which is a huge social, economic and Public Health problem. Tell me what its like to have a conversation with a mother and tell her that her baby has micrcrephaly. Its a situation with a lot of stress, panic, worry and insecurity, she told me. Thats because these parents and even Health Experts here are trying to figure o o what services these infants will need. Gave Public Health officials the right to enter any home or business to try to eradicate mosquito breeding grounds. Scott, well be reporting on this in the dame to come. Pelley jon lapook in brazil for us tonight. Jon, thank you. Amtrak is trying to figure out what hit a highspeed acela train last night in philadelphia. Whatever it was, it gashed a window and the train was taken out of service. Nobody was hurt. This is eerily similar, though, to last may when a commuter train was hit by something just before an amtrak regional train crashed in philadelphia. That crash killed eight and injured nearly 200. And today federal investigators gave us an update onn their investigation. Heres kris van cleave. Reporter newly released pictures taken from train 188s dash cam a show the moment the speeding train left the tracks. Engineer braraon bostian told investigators about a minute before the accident he realized he was going ten miles too slow his next memory was feeling as though i was going too fast around a curur. Ththtrains event recorder found bostian applied full throttle oy approximately a mile and a half from the curve. The train reached 106mph before bostian hit the emergency brakes. He said, i remememr holding on to the controls tightly and feeling like, okay, well, this is it, im going over. Toxicology reports found no evidence of drugs or alcohol in bostians blood, and he was in the using h h cell phone at the time of the crash. Lawyer tom kline represents several of the hundreds who were injured. The train was being operated at 106mph and there was a system that could have been in place and in fact was in place going the other way on the tracks which could have prevented it. Reporter that technology, positive train control or p. T. T. , is now active along amtraks heavily used northeast corridor linking boston to washington, d. C. Im going to try and put full power on the train here and see how fast i can do. Reporter amtraks chris jajadzinki showed us how p. T. C. Now, what happened here is this. Traction blocked. Its taken away all the power in the locomotive. Now its applying the brakes. Reporter so regardless of what you do. I cant do anything. The computer has taken over. Reporter investigators found no issues with the train, the tracks or the signals. Scott, w wstill dont know definitively if and when an object may have struck the trains windshield and if that could have contributed to the crash. A lawyer for bostian declined to comment. Pelley at 106, that was double the speed limit on that curve. Kris, thanks very much. One of the super bowl quarterbacks addresses a report that he used a bned substance. And danger on the high seas when the cbs evening news continues. And those in megared krill oil. Unlike fish oil, megared is easily absorbed. Which makes your heart, well, megahappy. Happppr still, megared is proven to increase omega3 levels in 30 days. Megared. The difference is easy to absorb. If youre taking multiple medications, does your mouth often feel dry . A dry mouth can be a side effect of many medications. But it can also lead to tooth decay and bad breath. Thats why theres biotene, available as an oral rinse, toothpaste, spray or gel. Biotene can provide soothing relief and it helps keep your mouth healthy too. Remember, while your medication is doininyou good, a dry y uth isnt. Biotene, for people who suffer from a dry mouth. You cant predict. The market. But at t. 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And i welcome that investigigion. And i understand when an allegation is made that the nfl has no choice to investigate it. I get that. But i can tell you what theyre going to find, a big fat nothing. Its been completely fabricated as far as the allegations of what they suggested that i did. Its been nothing but pure junk, and i welcome that investigation. So i think that will start right after the season. The quarterback on the other side on sunday, cam newton, oh, boy, hes fun to watch. Do you know that last week his longest run was 14 yards and yours was 12 . The difference is it took him, you know, 1. 2 seconds the make 14 yards. It took me ten seconds to get 12 yards. You had the use the clock. Im glad you pointed that out. It sure felt like i ran a lot longer. It fell like a 30yard run. I only got 12 . Pelley you can see the interviews with Peyton Manning and the panthers cam newton this sunday on cbs during coverage of super bowl 50. The pregame begins at 2 00 eastern. 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Photographsshronicling iowas caucuses from jimmy carter to ted cruz. Theres john kerry on the floor and the bench, al haig with a pig let, john mccain, back and front, two marco rubios and two joe bidens 20 years apart, bushes father and son and son, and the clintons, then and nowow the thing about iowa is it can really make a candidate. It can bring somebody like jimmy carter to National Prominence or even obama when he was here. And with deant washe opposite. It sort of doomed his campaign. Reporter this is your picture . This is my picture. Reporter former des moines rister photogrgpher lowest point. And then were going the washington, d. C. , the take back the white house. Yeah reporter todayay wells is the curator of this exhibit. We started shooting. We knew something was different. We knew something was happening. Reporter he didnt ask for a copy ofhis picture, dide . N n that i know of. Reporter Mike Huckabee visits a barbershop and jams Michelle Bachmann holds a side of beef. I think we were wondering why she decided to visit the meat locker. Reporter there are protests and arrests, and a flag is here in abundance. Mitt romney the candidate always seemed freshly pressed, and on caucus night four years ago, so was thing from at his premature victory rally. Photographer Christopher Gannon spotted it. This gentleman came out and plugged in a aron, and im thinking to myself, what is going on here. You can ask about a lot of these amazing photos, and o of the great things aut the caucus is that there will be many more to come. Dean reynolds, cbs news, des moines. Pelley and thats the cbs evening news for tonight. Well be back with updates on the Iowa Caucuses beginning at 8 00 eastern, 7 00 c ctral. For all of us at cbs news all around the world, im scott pelley. Well see you again soon. Captioning sponsoror by cbs cbs 2 news, caucus countdown. Right now on cbs2 news caucus count down. After months of campaigning iowans finally get their say. We have live reports from across the state. Plus Winter Weather on a move. The storm looks big. Yo you ouldnt let it worry you if you are headed to the caucuses tonight. Right now skies are clear and calm across the region. But its not expected to impact tonights caucuses. It will however be a much different picture by tomorrow. Cbs2 chief teorologist terry swails lead us. I promise this is going to be a chal he canning forecast because wool see the storm track in eastern iowa meaning differenenareas wiwi get different weather and some a lot more snow than others and the storm is coming together tonight down to the south of us here. Up. Nebraska and parts of cairns and rain trying to develop down here in missouri and by the time that reaches our southern counties later on tonight, that will at least for a while switch over to snow. So we think most of the precipitation around here will hold off until late tonight. Probably 3 or 4 in the morning before things cook in our southern counties and then that will be around occasional basis through wednesday morning. But its going to be our northern and northwestern