DES MOINES, Iowa -- After all the ads, rallies, and canvassing, now there's nothing left but for Iowa's voters to finally have their say Monday night at the critical first-in-the nation caucuses.
A win for Sanders would be a major upset that could carry his insurgent candidacy deep into the spring, while a win for Clinton would blunt Sanders' rise and help put her on a glide path to the Democratic nomination.
Clinton's first presidential campaign was derailed when she lost here in 2008, when Barack Obama -- another insurgent candidate favored by young people -- swamped her at the caucuses. This year, however, Sanders faces a number of challenges that Obama did not.
See photos of Hillary Clinton campaigning ahead of the Iowa caucuses
It's a cliché, but this time it's true: The race will likely be decided by turnout. If the total number of caucus-goers is close to the 240,000 that showed up on the Democratic side in 2008, Sanders could win. But if turnout is closer to the 125,000 that came out in 2004, Clinton is the favorite.
Clinton's campaign began in the state 15 months ago after she drove across the country in what she affectionately dubbed the "Scooby Van" for a series of tiny roundtable events.
It ended with a massive rally in Des Moines of 2,600, one of her largest in the state, as Clinton made her closing pitch about her readiness for the job and ability to beat Republicans.
Clinton was joined on stage by her husband, former President Bill Clinton, and their daughter, Chelsea, who had flown into the state to give the candidate a final boost.
Former Sen. Tom Harkin, one of Clinton's most powerful backers in the state, told the crowd he could "smell a lot of victory in the air."
Meanwhile, across town, 1,700 people packed into a gymnasium to see Sanders one more time on the eve of the caucuses. He began by thanking Iowans for their hospitality and for giving his unexpected candidacy a chance, before moving on to deliver his stump speed.
See photos of Bernie Sanders supporters
With Clinton narrowly ahead in recent polls, Sanders' campaign is lowering expectations and preparing spin a narrow loss as a win, given that he started so far back.
At the Sanders rally, supporter after supporter took the podium to remind voters of how far they've come, but no one with the Harkin's stature predicted victory. "Because of you, we ain't 50 points down anymore, are we?" said Pete D'Alessandro, Sanders' top official in the state.
"At the end of the day, I think in terms of the division of delegates, whether you win by two points or you lose by two points, it's not going to matter a whole lot," Sanders told NBC's Chuck Todd on "Meet the Press" earlier in the day. Later, at an event in Marshalltown, Sanders called the race a "tossup."
Over the weekend, there was a last minute push as the campaigns mobilized their massive get-out-the-caucus machines, the two largest operations in the state of either party.
See photos of Iowa ahead of the caucus
Four thousand Sanders volunteers knocked on 112,000 doors across the state Saturday and Sunday, according to an aide. Clinton's campaign, meanwhile, rang doorbells at even more than 125,000 doors, an aide said, and campaign manager Robby Mook even hit the streets to engage voters.
The Clinton campaign claims more than 4,200 trained precinct captains and team members are in place for caucus night, while the Sanders campaign says it has 2,626. Either number will should be plenty to cover the 1,681 Democratic precincts across the state.
Earlier in the day, Sanders announced that he raised a whopping $20 million in January alone, and that the campaign had received a total 3.25 million individual contributions.
The candidates have no scheduled events Monday, leaving a lengthy calm before the caucuses, which kick off at 7:00 p.m. CT sharp and continue for two hours. As the results come, Sanders and Clinton will rally with supporters, hoping for some good news.
Before the night is over, however, the candidates will quickly flee the state to which they've devoted so much time and energy to make a beeline for New Hampshire, with it's first-in-the-nation primary now just 10 days away.