plus the half-time show that has everybody talking. this is the "cbs evening news" with norah o'donnell reporting from the nation's capital. >> o'donnell: good evening, and thank you so much for joining us. as we come on the air tonight, it's democracy in action. caucus-goers are beginning to gather at nearly 1,700 school gyms and community centers all over iowa. by the end of the night, we should know which candidate or candidates have scored the first points in the race for the democratic presidential nomination. 41 delegates are up for grabs. now that's just 1% of all pledged delegates that will be awarded during the democratic primary process, but iowa is all about seizing momentum. the top seven candidates have spent a combined 400 days campaigning in the hawkeye state. our cbs news battleground tracker has joe biden and bernie sanders neck and neck, but with very different bases of support. pete buttigieg and elizabeth warren are also still in the hunt. our team is covering every angle of the caucuses tonight, but we're going to begin with ed keefe at sanders' headquarters in des moines. ed? >> reporter: norah, good evening. candidates have held more than 2,200 events combined in this state over the past year, and a record crowd is expected as iowa puts the first points on the board of campaign 2020. the candidate to watch closest tonight is bernie sanders. moments after the impeachment trial wrapped for the day in washington -- >> on my way to iowa. >> reporter: -- bernie sanders raced back to iowa for what he hopes is a victory party. ( cheers and applause ) over the weekend, sanders projected confidence. >> tomorrow night is the beginning. it is the beginning of the end for donald trump. >> so you're going to have... >> reporter: he has relied on thousands of volunteers who knocked on 500,000 doors last month alone. >> that's an extraordinary accomplishment. >> reporter: if sanders does it, he'll do it by turning out younger and first-time caucus- goers and latinos who made up just 4% of the caucus vote in 2016. but with the race so tight, sanders is hoping to increase that number, which is why the first piece of mail his team sent iowa voter was in english and spanish. moderates worried about sanders win are blanketing the airwaves warning he could lose to president trump. >> i do have some concerns about bernie sanders' health considering he did have a heart attack. >> reporter: voting begins tonight when iowans meet at nearly 1,700 caucus sites in 99 counties. they'll sort themselves by candidate, and each must earn at least 15% to be what's called "viable." if a candidate falls short, other campaigns can scramble to earn their supporters votes. >> reporter: i'm nikole killion with the biden campaign. the former vice president upbeat as he surprised staff with pizza. cautiously optimistic, he'll deliver tonight even if he doesn't finish first. >> we'll survive all the way through this whole thing. >> reporter: still a third or fourth-place result here would be considered a major setback. he's arguing experience and electability matter. >> the next democratic president of the united states has to be prepared to command the world stage, to lead our armed forces. >> reporter: one area of concern tonight is biden's get out the vote operation, which lags behind the other top contenders. the campaign is counting on turnout in rural areas and among working-class voters in eastern iowa. they're hoping to woo caucus- goers like abbott laprade, who is deciding between amy klobuchar and pete buttigieg but not ruling out biden as his second option. >> why biden? >> you know, again, i think it just comes down to who can beat donald trump. >> reporter: the campaign believes tonight will be close, but if biden doesn't land in the top tier, aides will argue that iowa is only the beginning, not the end of the primary process. norah. >> o'donnell: nikole, thank you. let's bring in major garrett, our chief washington correspondent who is in des moines tonight. so major, is it possible that by the end of the night multiple candidates will claim victory? >> reporter: it's possible even though the iowa democratic party says there is just one winner tonight, the candidate who claims the highest number of delegates. but that doesn't mean campaigns won't fight over the numbers, because there are three numbers to look at. here's the first number: everyone's first choice. once they arrive at the caucus site the second number, when caucus- goers realign if their first choice didn't meet the minimum threshold of 15%. the third number, actual delegates allocated per candidate. bernie sanders campaign thinks he will do well on that first- choice number and may point to that as a big victory even though the delegates awarded to candidates or realignment number may move to be much closer. >> o'donnell: while iowa is not representative of the country, it does give an early sense of a campaign's strength. so, what have you learned? >> reporter: energy is through the roof. record turnout is expected. here's one way to think about it: seven different campaigns each have 100 or more staffers on the ground. in 20 years of covering the caucuses, i have never seen that kind of commitment to ground organizing. the other thing that strikes me, this is the nicest iowa caucus i have ever seen. democrats do not attack each other, why? because party unity is paramount. they want to bring the party together once the nominee is known. norah. >> o'donnell: major, thank you. much of iowa is rural and filled with family farms and about half are owned by women. these are difficult times for many of them. janet shamlian has more on their struggles and hopes. >> i'm going to go in and vote for tom steyer. >> elizabeth warren. >> i'm pretty much undecided. >> amy klobuchar. >> reporter: these four women all have passion for politics. >> i think all of them can beat donald trump. >> reporter: ellen walsh-rosmann is a mother of two who thinks elizabeth warren can revitalize farm country. >> i want to make sure that people my age, my peers are coming back and they have a reason to come back to rural america. >> reporter: chris henning has only decided she's not supporting joe biden or bernie sanders. >> my issues are their age, their health, and their stamina. >> reporter: they're too old? >> they're older than me, and i think i'm too told run for office. >> reporter: like many of her rural neighbors, healthcare is an issue for billie wilson. >> in small towns, most people don't have anybody that pays their insurance, even this t small businesses don't provide. everybody is in the same boat. >> reporter: lavon griffieon is concerned about the economy. >> in 2012 we had soybeans at $15. now they're at $8. that's half. >> reporter: caring for land and livestock requires lots of help. they say hiring immigrants is a critical issue. >> they do the work no one wants. they work at the dairies. they do the ruffing. they do a lot of-- >> they're not stealing our jobs. >> no, they're not stealing our jobs. >> janet shamlian, cbs news, ankeny, iowa. >> o'donnell: and we'll have updates tonight right here on cbs. breaking tonight, health officials in china are reporting dozens more deaths from the deadly coronavirus. the death toll now is at least 426. the world health organization is warning the outbreak could soon be large enough to be classified as a pandemic. 11 cases have been confirmed here in the u.s. mola lenghi now on plans to bring hundreds more americans home from china. >> reporter: ten days, that's all it took to build this hospital to treat coronavirus patients in wuhan, china. video from chinese state tv shows stock supplies to treat the unprecedented health crisis. >> everybody is feeling really antsy about this getting out. >> reporter: american priscilla dickey and her daughter hermione are stuck in wuhan and desperate to come home. the u.s. state department is organizing more charter flights out. cbs news has learned four military bases will be used to quarantine evacuees while they're monitored for symptoms. >> it's one thing to have this in your own home, it's a total other one where you're kind of isolated by yourself. >> reporter: today the c.d.c. confirmed the second case transmitted person-to-person, the spouse of a wuhan traveler. 83 tests are pending, including three in new york city. >> it seems the virus spreads fairly easily when you're not isolating cases quickly. >> reporter: dr. mark mulligan is head of infectious diseases at nyu langone in new york city. he's concerned about the unknowns. >> a person without symptoms seems to have transmitted the virus. how often does that happen? >> reporter: is there a risk for overreaction? >> this is a time for reaction and for awareness to make sure we know the very latest things happening. >> reporter: one of those three suspected new york city cases being treated and evaluated in isolation here at bellevue hospital in manhattan. and just this afternoon, we learned that about 100 princeton university students who recently traveled to china are now being monitored. their symptoms are being monitored, and some have even asked to self-quarantine, norah. >> o'donnell: that's significant, mola. thank you. tonight at least one senate democrat says he's still not sure how he'll vote at president trump's impeachment trial. west virginia's joe manchin does say the president should at least be censured by the senate. today senators heard closing arguments in the case. nancy cordes reports tonight from capitol hill. >> the senate can still do the right thing. >> reporter: the house impeachment managers closed the trial with a warning about president trump. >> what are the odds if left in office this he will continue trying to cheat? i will tell you: 100%. he is who he is. truth matters little to him. what's right matters even less. if you find that the house has proved its case and still vote to acquit, your name will be tied to his with a cord of steel and for all of history. >> reporter: the impeachment trial took up 82 hours on the senate floor. to the end, the president's legal team insisted he had done nothing wrong. >> the president did not condition security assistance or a meeting on anything. >> the only appropriate result here is to acquit the president and to leave it to the voters to choose their president. >> reporter: it would take a two-thirds senate vote to remove the president from office, and most, if not all republicans, are poised to acquit. >> the enthusiasm with which the house managers have sought president trump's removal is completely and inarguably divorced from reality in the heartland. >> reporter: tonight republicans are urging this president not to gloat about his impending acquittal during his state of the union address here on capitol hill tomorrow night. but privately, norah, they acknowledge that it would be unlike him to stay silent. >> o'donnell: all right, nancy, thank you. today rush limbaugh, one of america's leading conservative voices for the past several decades, shocked listeners with a message about his health. manuel bojorquez on limbaugh's announcement. >> i have been diagnosed with advanced lung cancer. >> reporter: that's how the cigar-loving rush limbaugh broke the news to his listeners. >> there are going to be days that i'm not going to be able to be here because i'm undergoing treatment or i'm reacting to treatment. >> reporter: it's not the first time limbaugh has shared his personal struggles. in 2003, he announced he was battling opioid addiction. professionally he's best known as a champion of conservative causes. >> we have a major immigration problem. >> reporter: and controversial commentary. >> in this commercial he's exaggerating. >> reporter: in 2006, he alleged actor michael j. fox exaggerated the effects of his parkinson's disease in an ad for stem cell research. limbaugh, a staunch supporter of president trump, said he would be gone the next few days as his doctors figure out his treatment. manuel bojorquez, cbs news, miami. >> reporter: tonight we're getting a look at some dramatic video from a deadly terror attack in london. the suspect had just been released from prison after serving only half his sentence on terrorism charges. elizabeth palmer reports tonight from london. >> reporter: cell phone video captures the immediate aftermath. the terrorist, sudesh amman, has been shot. just yards away, one of his victims lies bleeding on the sidewalk. undercover officers keep their weapons trained on amman until back-up arrives. and then fresh urgency when it look like he may have an explosive vest. >> there was something strapped to his chest. a silver-- it was kind of like a silver canister. >> reporter: but it turns out to be a hoax. amman had been under surveillance. he'd done jail time for islamist-related crimes and had been released just days ago. for londoners, it's the second such attack in just over two months. usman khan stabbed two people to death in november before the police shot him on london bridge. khan, like amman, had just been patrolled without anyone assessing either man for violent extremist potential. an outraged public now has britain's government scrambling to change the law so that never happens again. elizabeth palmer, cbs news, london. >> o'donnell: winter storm and blizzard warnings are posted tonight across much of the rocky mountains. utah, colorado, wyoming, idaho, and montana are all getting walloped. the storm is expected to push across the country this week, dumping snow, ice, and rain in the central u.s., the south, and the northeast. there is still much more news ahead on tonight's "cbs evening news." why a fighter jet was sent up to check on a passenger jet that was circling an airport. what researchers have learned about the risk of heart disease in women going through menopause. and the unofficial m.v.p.'s of the super bowl. why everybody is talking about that half-time show. you make time... when you can. but sometimes life gets in the way, and that stubborn fat just won't go away. coolsculpting takes you further. a non-surgical treatment that targets, freezes, and eliminates treated fat cells for good. discuss coolsculpting with your doctor. some common side-effects include temporary numbness, discomfort, and swelling. don't imagine results, see them. coolsculpting, take yourself further. go to coolsculpting.com for a chance to win $25,000. for the past 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