Iowa often acts more as a bar bouncer than a kingmaker, culling the field but not anointing a leader. Candidates strive to finish in at least the top three to seize some momentum as they speed toward later nominating contests.

But there are reasons to question whether that thinking still applies. Four candidates are closely clustered at the top of the polls. National front-runner Joe Biden, Pete Buttigieg and Senator Elizabeth Warren are all polling well enough to have a chance at securing delegates.

“You may need more than a four-passenger car for all these folks to get out of here,” said Iowa Democratic Party Chairman Troy Price at a Bloomberg News breakfast of political reporters Friday. He said as many as six could move on, including Amy Klobuchar and Andrew Yang.

A top finish would give Sanders, a senator from Vermont, an early lead going into New Hampshire, a state that gave him a 22-point win over Hillary Clinton in 2016 and a consistent lead in 2020. And wins in both of the first two contests would provide him undeniable momentum. But he is a polarizing figure in the Democratic Party, with both fierce supporters and voters who find his ideas too liberal to be viable.

That could prompt a “Stop Sanders” movement — putting increasing pressure on lower-polling candidates to drop out and throw their support behind a more moderate alternative.

“Things tend to boil down to a person who’s leading, and the alternative to the person who’s leading,” said political scientist Josh Putnam, an expert on party nominations who runs the blog Frontloading HQ. “There are differences in every cycle, but these things tend to operate in a similar fashion.”

Yet it’s not like any of the three moderates in the race — Biden, Buttigieg or Klobuchar — are ready to fold and anoint one of the others as the Bernie-stopper.

The most recent RealClearPolitics average of Iowa polls shows Sanders leading Biden by 3.2 percentage points. But polls aren’t unanimous: One Monmouth poll Wednesday had Biden leading by 2 points, well within the margin of error.

Also complicating the storyline are rule changes that will give greater transparency into the performance of the entire field. In previous years, Iowa reported only the number of state delegates each candidate was expected to win. This time, the party will reveal how many Iowans backed each candidate in the first round of voting — even if that candidate didn’t meet the 15% threshold that’s a major hurdle for lower-polling candidates.

Those reporting rules, written in the aftermath of Sanders’ complaints about his narrow loss in Iowa in 2016, could ironically blunt the impact of his finish this year. Candidates who come in second, third or even fourth in the final tally could claim much better standing if they do well in the first round.

Still, Iowa punditry is partly an expectations game. A front-runner who stumbles into second place can be judged more harshly than a second-tier candidate who unexpectedly comes in third. So the candidates are already working to blunt any blow from a poor showing.

Despite investing early and extensively in an Iowa organization, Warren is not polling well, and her campaign is trying to make clear she will carry on regardless.

“We expect this to be a long nomination fight and have built our campaign to sustain well past Super Tuesday and stay resilient no matter what breathless media narratives come when voting begins,” campaign manager Roger Lau wrote in a memo last week.

Yang said this week that regardless of how he finishes in Iowa, he expects to do even better in New Hampshire — where the state’s libertarian streak might be more receptive to his message.

Iowa awards 41 delegates to the Democratic National Convention, or just a little more than 1% of the total delegates. But its importance far outweighs the delegate count, given it is the first actual votes of the 2020 election year and gives Americans a chance to see which candidates are living up to their claim of electability.

A Front-loaded Calendar

Most candidates may have little incentive to drop out after Iowa, regardless of their showing, given that contests in New Hampshire, Nevada and South Carolina quickly follow in February.

Biden has built a firewall in South Carolina’s Feb. 29 primary, where his support among black Democrats could make up for any early stumbles. And it’s not just Biden: The Martin Luther King Day events there this month became virtually mandatory for any serious candidate for president.

“South Carolina has come into its own this time,” said Elaine Kamarck, author of “Primary Politics: Everything You Need to Know about How America Nominates Its Presidential Candidates.” “It’s the last, best stop before Super Tuesday.”

Super Tuesday — a 14-state primary on March 3, three days after South Carolina — will award 34% of all delegates. And unlike Republicans, who allow states to award delegates on a winner-take-all basis, Democratic delegates are awarded proportionally. Any candidate getting at least 15% — statewide or in a congressional district — is eligible to win delegates.

That could increase the likelihood that the front-runner could divide and conquer the opposition.

“Let me put it this way: The Democrats can choose to repeat the Republican folly of 2016,” said Kamarck, a member of the Democratic National Committee’s rules committee. “They all stayed in the race. They did not rally around the alternative, and Donald Trump became the nominee.”

Another harbinger of a drawn-out nomination fight: money.

The importance of Iowa is as much about fund-raising as it is about delegates, said Jeff Link, a Democratic Iowa political strategist.

Klobuchar, a senator from neighboring Minnesota, may feel the most pressure if she doesn’t do well, but Warren and Buttigieg could also struggle with donors if they have a poor showing,” Link said.

But candidates sustained by small-dollar donors — like Sanders and Yang — can keep going as long as the recurring monthly donations continue.

“If Bernie got seventh, he’d move on,” Link said.

And the two billionaires in the race — Tom Steyer and Michael Bloomberg — have already spent hundreds of millions on states that vote after Iowa and New Hampshire. Bloomberg is skipping the early states entirely and isn’t seeking any delegates until March 3.

Bloomberg is the founder and majority owner of Bloomberg LP, the parent company of Bloomberg News.

Age, too, might be a factor in keeping more candidates in the race longer. Younger candidates often have more incentive to drop out early in the interests of party unity — and their political futures. For candidates over 70 — Sanders, Biden, Bloomberg and Warren — waiting four to eight years for another chance at higher office is an unlikely option.

More must-read stories from Fortune:

—2020 candidates’ positions, and records, on economic issues that affect women
—Bernie Sanders wants the future of the far left to be female. Is that enough?
—Michael Bloomberg’s radical plan to cut prescription drug costs
—Fortune Explains: The debt ceiling
—Millions have been purged from voter rolls—and may not even realize it

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