What each candidate needs to do in the Iowa caucuses

In January 1980, George H.W. Bush narrowly won the Iowa caucuses over front-runner Ronald Reagan. Bush had trailed Reagan by 9 percentage points in the final poll of the Republican contest, but he triumphantly beat expectations. Having won, Bush claimed he had the "Big Mo" — momentum — moving forward. And while Bush didn't win the GOP's presidential nod, his Iowa performance put him on course to become Reagan's main rival, and later, the vice presidential nominee.

As the 1980 case demonstrates, Iowa has helped shape the results of presidential contests since the dawn of the modern nomination system in the 1970s. In tandem with New Hampshire's primary, the Iowa caucuses have provided a pivotal opportunity for candidates to exceed expectations from the start, which in turn can boost their fortunes down the line. The threshold for what could be considered a good or bad performance is a moving target influenced by poll numbers, political media and a candidate's own expectations-setting. Beating those marks can raise a candidate's viability in the eyes of the press, donors and voters, precipitating increased and more positive media coverage, stronger fundraising and greater support in later electoral contests.

Today's Republican caucuses could once again help make or break presidential candidacies. Entering the race, former President Donald Trump holds a more than 30-point lead in 538's Iowa polling average, and few expect him to have much trouble winning. But while Trump's campaign can withstand a poor early performance in Iowa and remain on track, his opponents' trajectories are more likely to be sharply affected by how they perform this evening. This is especially true of Florida Gov. Ron DeSantis and tech entrepreneur Vivek Ramaswamy, who have largely staked their candidacies on success in Iowa. On the other hand, a stronger-than-expected showing from former U.N. Ambassador Nikki Haley could cement her position as Trump's principal opponent heading into New Hampshire's primary on Jan. 23.

How the public, media and political insiders interpret tonight's vote tallies will come down in part to how each candidate performs relative to expectations heading into the caucuses. Here then is a look at what kind of result each Republican probably needs to exceed these expectations and capture the "Big Mo" — or how Iowa could prove a death knell for their campaigns.

Donald Trump: Hold serve

Trump enters the caucuses as the prohibitive favorite for the Republican presidential nomination. In Iowa, any result other than a victory would rank among the most shocking results in the modern history of presidential primaries.

But being such a clear front-runner makes it tough to exceed already high expectations and gain an even more dominant position in the race. Trump himself has reinforced the idea that he has a big lead while also trying to keep his supporters motivated to turn out. In a campaign visit to Iowa last week, he told backers that they needed to "forget polls that show we're 35 points up" and "pretend we're one point down." His campaign has also sought to lower high expectations by emphasizing that no Republican has won Iowa by more than about a dozen points — back in 1988, Bob Dole won by about 13 points.

Considering Trump's position, his main goal will be simply to meet expectations by achieving a sizable win, one with at least 50 percent of the vote. If Trump wins with less than a majority, that could provoke story lines about an underwhelming victory ahead of New Hampshire, where he holds a smaller 11-point polling edge over Haley. Conversely, if Trump overperforms his polls and wins Iowa with close to or even more than 60 percent, it would likely produce headlines about his dominance and add to the sense of inevitability about his nomination.

But regardless of how big or small his victory proves to be, Trump will remain a heavy favorite for the nomination. After all, he retains the strongest favorability rating of any GOP contender among Republican voters. And much of the party has rallied to him, including a recent surge in endorsements by Republican members of Congress looking to secure their seat on the Trump Train before it leaves the station to win in Iowa.

Ron DeSantis: Be this year's comeback kid

DeSantis and Haley are vying to be the main alternative to Trump, but it's quite possible that DeSantis won't last much longer unless he puts in a solid Iowa showing. After running in second place in Iowa throughout the campaign season, DeSantis fell to third place in our polling averages for the first time on Thursday, and is now at 16 percent, just behind Haley's 19 percent. And with Haley surging in New Hampshire, there's little doubt that DeSantis must claim second in Iowa to remain viable — finishing third behind Haley could break the back of his campaign.

Such expectations rest in part on the moves of DeSantis's campaign and allies, who've gone all-in on Iowa since DeSantis's grip on second place loosened late last summer. In October, DeSantis moved a large part of his mostly Florida-based campaign operation to Iowa. In November, he earned the much-coveted endorsement of Iowa Gov. Kim Reynolds and support from noted evangelical leader Bob Vander Plaats. And in early December, DeSantis claimed to have visited his 99th of Iowa's 99 counties, completing "the full Grassley" — a reference to longtime Sen. Chuck Grassley. Meanwhile, Fight Right, now the principal super PAC backing DeSantis on the airwaves, has focused its spending on Iowa, as has DeSantis's campaign, which in November entirely cut its ad buys in New Hampshire.

As recently as early December, DeSantis said "we're going to win Iowa." Yet as his campaign has faltered, he has tried to recalibrate expectations. This month, DeSantis has deflected questions about his Iowa standing by emphasizing the primary is a "long process" and that he needs to win a majority of delegates to become the GOP nominee. Perhaps cagily, he also said that he "kind of likes being underestimated." Tamping down expectations is a time-honored political tactic, whether talking about caucus votes or an upcoming debate performance.

For DeSantis, one hope is that his field operation will provide him with a boost to outperform his poll numbers. Never Back Down, the main super PAC backing DeSantis this cycle, has carried out a promised $100 million ground game that included knocking on nearly 1 million doors in Iowa. This could be a key differentiator for DeSantis because Haley didn't have much of a field operation in Iowa until late in 2023. Haley also may have handed DeSantis a last-minute gift when she said earlier this month that New Hampshire voters will have a chance to "correct" Iowa's electorate. DeSantis and his surrogates have tried to use this to ding Haley, including an attack ad from Fight Right.

Long story short, DeSantis's best-case scenario is a result that earns him the "Comeback Kid" moniker that Bill Clinton famously gave himself after finishing second in the 1992 New Hampshire primary. Even though beating Trump looks outside the realm of possibility, beating expectations (and Haley) with a clear runner-up performance in the mid-20s is feasible.

Nikki Haley: Stay on an upward trajectory

There's an old saying that "there are only three tickets out of Iowa" — that is, the contest usually winnows the field — but Haley could burn DeSantis's ticket if she finishes in second place ahead of him tonight. Haley's poll numbers have been on the rise, and she could also benefit from former New Jersey Gov. Chris Christie's departure last week because his supporters were most likely to name Haley as their second choice. That's a much bigger story in New Hampshire, where Christie was polling in the double-digits, but his small group of Iowa supporters could also help make a difference in a close race.

Given Haley's greater emphasis on New Hampshire, though, her campaign has had the luxury of not feeling pressured to promise anything close to a win in Iowa. For instance, the lead strategist for Stand for America, the main super PAC supporting Haley, said in early January that he didn't know if Haley could get second, but that doing so would put her in "a great position to win" in New Hampshire. Back in late November, her campaign considered the prospect of finishing second in Iowa as a huge win for Haley because it would seriously damage DeSantis and set her up nicely for the subsequent contests in New Hampshire and her home state of South Carolina.

Still, with Haley's obvious upward trajectory in the race, expectations for her performance in Iowa have also risen — to the point that she may need to finish second to keep her momentum going. And while she's sought to keep expectations low in the state, she's still invested big. Her campaign and allied outside groups have not only outspent DeSantis down the stretch, they've also outdone both DeSantis and Trump in total spending throughout the campaign in Iowa, according to ad spending data from AdImpact. Tellingly, however, the Trump campaign recently began focusing its attacks on Haley rather than DeSantis, as it became clear that she might be Trump's most dangerous opponent — a development that could stall some of Haley's progress. And Haley's recent slip-ups on the trail could cause doubts in some Iowa voters' minds, including her line about New Hampshire needing to "correct" Iowa and her inability to name slavery as the cause of the Civil War at a late December event.

Bottom line: Haley's rosy but not unrealistic ideal is a clear second-place showing in Iowa that effectively ends DeSantis's campaign and carries her into New Hampshire on a wave of glowing headlines. Although Trump would still hold a clear edge in the Republican nomination contest, the media's desire for a competitive horse race could help Haley if she can beat expectations in Iowa — generally speaking, the media is more likely to provide increased and positive press coverage to a strong runner-up than to a victorious front-runner.

Vivek Ramaswamy: Show signs of life

Ramaswamy is the only other candidate of note left in the GOP contest, and while he has not looked remotely competitive since he enjoyed a late-summer surge in the polls, he could use a solid Iowa performance to justify staying in the race. Ramaswamy has even surpassed DeSantis in his focus on Iowa, to the tune of spending almost 90 days on the ground and holding more than 300 events in the state — more than double the number DeSantis has held. Back in late October, Ramaswamy said he had a good shot at second or third place in Iowa. Yet a third-place finish would be a shock at this point, considering he's polling at slightly above 6 percent in Iowa, roughly 10 points behind DeSantis. However, Ramaswamy's time and effort could pay dividends with a better-than-expected showing — say, 10 percent or higher.

That would be a pretty remarkable result considering some of the recent developments in his campaign. In late December, Ramaswamy's operation stopped running television ads in Iowa just weeks before the caucuses. And while it resumed running ads about two weeks later, interrupting ad spending in the place where your campaign has invested the most time and energy is never a great sign. He also failed to qualify for the Iowa debate held on Jan. 10, a sign of his polling weakness and increasing irrelevance in the campaign.

With all this said, Ramaswamy has self-funded a substantial portion of his campaign, so if he fails to beat expectations, he could still choose to hang around. It's only a tea leaf, but Ramaswamy recently sold $33 million in stock and promised to invest some of the funds into his campaign. So he may stay in the race, one way or another.

Don't rule out surprises

Presidential primary polls have larger average errors than general election polls, so we shouldn't rule out a candidate substantially under- or outperforming their polling numbers. Since 2000, the average error in primary polls compared to the final electoral margin is 9 points, more than twice that of general election polls. This is because nomination races are more dynamic contests. Voters are choosing among candidates from the same party, so they don't have a candidate's party ID to default to when making a choice — they may like more than one contender and change their preferences at the last minute. Additionally, a candidate can drop out just before a contest, leaving insufficient time to gauge how that has affected the race.

One last-minute wrinkle this year has been the weather. Significant snowfall occurred in the days leading up to the caucuses, and temperatures across Iowa today will hover around 0 degrees or below. With deeply negative wind chills on tap when voters go to caucus this evening, a typically low-turnout event could involve even fewer voters this time around. It's difficult to gauge how that could affect the result, but at the very least, some less-committed potential caucusgoers might decide against braving the weather.

So while we expect Trump to win, it's best to remain cautious about what else could happen. What we do know is that at least one of Trump's opponents really needs to grab hold of the "Big Mo" tonight to have even a minimal chance of defeating him for the Republican nomination.