As presidential campaigns game out the final stretch before the Iowa caucuses, one major unknown variable threatens to gum up the equation: the looming impeachment trial of President Donald Trump.

The prospect of a potentially lengthy trial held in the U.S. Senate, stretching for six-day weeks and consuming almost every atom of the country’s political oxygen, hangs over every aspect of the Democratic presidential primary—particularly the next debate on Jan. 14, the last major public engagement for Democratic presidential hopefuls before the first votes are cast.

Five of Trump's jurors are currently running for president, including three of the five candidates who have qualified for the debate: Sens. Amy Klobuchar of Minnesota, Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts. A fourth—former Vice President Biden—has been floated by Senate Republicans as a potential target of a subpoena to testify in the trial, leaving Democrats with the prospect of former South Bend Mayor Pete Buttigieg debating himself for three hours.

The Democratic National Committee has been quietly working on a contingency plan for rescheduling the debate in the event of an impeachment-related scheduling complication, rather than cancelling it altogether.

“If a conflict with an impeachment trial is unavoidable, the DNC will evaluate its options and work with all the candidates to accommodate them,” Democratic National Committee communications director Xochitl Hinojosa told The Daily Beast.

But as negotiations between Senate Democrats and Republicans over the trial’s rules and proceedings remain at an impasse, and the Democratic National Committee keeps a potential contingency plan close to the chest, candidates are preparing for the possibility that those accommodations will come at the very last minute.

“Being caught in a tug-of-war between Nancy Pelosi and Mitch McConnell is not where you want to be two weeks from Iowa,” said one campaign adviser for a candidate who has qualified for the debate, which is set to be held at Drake University in Des Moines. “We’re of the mind that it’s not a sure thing until they’re literally standing onstage.”

In public, none of the candidates set to serve as members of Trump’s jury have expressed concern about the conflict between the debate and their constitutional duties as senators. Speaking in Rochester, New York, last month, Warren told reporters that “there are some things that are more important than politics,” and that she would be at the impeachment trial regardless of the implications for her campaign.

Speaking to reporters on the trail last month, Sen. Cory Booker’s campaign manager Addisu Demissie said that while the feasibility of hitting the trail during an impeachment trial isn’t possible to determine until Majority Leader Mitch McConnell agrees on rules for the trial, the New Jersey senator is expecting a lot of red-eye flights at a minimum.

“We don’t really know how long it’s going to be, what time of the day it’s going to be, whether he can do stuff in the morning, then hop a train or a flight in the afternoon to get there in the evening, or vice-versa,” Demissie said. “We’re staying flexible.”

Others have proposed creative workarounds for being seated in the U.S. Capitol during the day and taking the stage in Des Moines hours later. Speaking on Face the Nation , Klobuchar floated the possibility of making appearances on Skype in lieu of in-person campaign stops.

“We have to have the debate, and if for some reason it doesn’t work… there’s plenty of other days,” said Klobuchar, who has bet the farm on a strong performance in Iowa. “There should be no excuses—I’m ready to debate at midnight if that’s what we have to do.”

But the pre-caucus calendar in Iowa is already packed to near-capacity. With blackout dates ranging from the National Football League playoffs and the Super Bowl—spread across four weekends, including the Sunday before the caucuses—to the Iowa Brown & Black Presidential Forum, to be held on Martin Luther King Jr. Day, Democrats have little wiggle room for a last-minute postponement.

All of this agita is moot, of course, until congressional leadership can determine when the impeachment trial will begin. House Speaker Nancy Pelosi has not yet sent the two articles of impeachment passed by the House of Representatives to the Senate, waiting instead for McConnell to send her rules outlining how the trial would proceed. The waiting game will continue at least until late next week, when the House returns from vacation.

For his part, McConnell has shown little interest in helping speed the process along. Asked by the Wall Street Journal when the Senate might return—thereby starting the impeachment trial—the Kentucky senator said that “it’ll be right around the time the bowl games end. How about that?” The College Football Playoff National Championship is currently scheduled for the day before the Democratic debate.

As for President Trump himself, the man at the center of the impeachment trial isn’t letting his own impeachment keep him off the campaign trail. Trump is scheduled to hold at least two campaign rallies this month, including one on the night of the Iowa debate.