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– The holiday break is wrapping up, but there doesn't seem to be an end in sight to the stalemate between House Democrats and Senate Republicans over how to hold President Donald Trump's Senate impeachment trial.

House Speaker Nancy Pelosi, D-Calif., is withholding the articles of impeachment from the Senate and not naming House lawmakers to prosecute the case (called managers) until Senate Majority Leader Mitch McConnell, R-Ky., agrees on the parameters of a trial that she views as fair. "We cannot name managers until we see what the process is on the Senate side," she has said. But McConnell has said that he's working in "total coordination" with White House lawyers and that there is no such thing as fair in a political body, so why even try? "This is a political exercise," he has said.

That means it's a real possibility that Congress comes back next week and there is no Senate trial starting up soon, as expected. So how could this impasse end? Here are four possibilities, ranked from least to most likely.

4. There is no Senate trial — at least not in 2020

Could there just be no Senate trial to acquit or convict Trump?

"Fine with me," McConnell has said about Pelosi holding back the articles of impeachment.

Or what if Democrats held back the impeachment articles and the naming of House prosecutors until Democrats won back the Senate in the 2020 elections? (Which, by the way, is a big risk. They'll need to win in states that voted for Trump in 2016.)

Or what if McConnell decided to hold a trial without the articles, or without House Democrats as prosecutors? That's really out there in terms of constitutional law, but everything about this impeachment process has been norm-breaking.

Why this might not happen: No Senate trial is the least likely option just because it's so far-fetched. The consensus among legal experts is that the Constitution requires a Senate trial to happen after the House impeaches a president. Senators decide whether to acquit or convict the president on the impeachment charges, and if they convict him, he's removed from office.

3. Pelosi gets her way

This means McConnell agrees at the outset to call witnesses.

There have been a couple of pieces of news over the holidays that could give Pelosi and Senate Democrats even more leverage to get what they want in a Senate trial.

A federal judge threw out a lawsuit that could have forced former national security adviser John Bolton to testify in the House's impeachment inquiry. (The House impeached Trump without waiting for this suit to play out.) So now, Democrats could argue the courts aren't going to weigh in and Bolton should be available to share what he knows.

Why this might not happen: It's hard to see McConnell suddenly acquiescing to Democrats' demands. It might sound cynical, but his mind-set is that he has a right to hold a trial however a majority of senators want, and that likely means however Republicans — and Trump — want.

2. McConnell gets his way

McConnell gets to hold the trial in a way that benefits Trump. He's not out there saying exactly how he wants that to look, but we could assume that means a quick one without any witnesses nor any new evidence.

McConnell isn't ruling out witnesses. But it appears he's doing everything he can to avoid calling them, so as to prevent people with potentially damaging information on Trump and Ukraine, like acting chief of staff Mick Mulvaney or Bolton, from testifying. He also likely doesn't want Trump to get his preferred way and have his lawyers cross-examine people like Joe Biden or the whistleblower.

Why this might not happen: McConnell controls the majority in the Senate. But this isn't the likeliest option because there's an argument that McConnell and Trump want the trial more than Democrats do.

1. They come up with some kind of compromise

But what would that look like given the loggerhead over witnesses? Josh Chafetz, a constitutional expert at Cornell Law, said there are smaller things senators could compromise on to get the trial started and then decide the big one later on.

"In other words, witnesses/no witnesses isn't a binary: there are a lot of smaller procedural trade-offs that can be made," Chafetz wrote in an e-mail.

That still doesn't solve the broader problem of how to break the impasse between Pelosi and McConnell over witnesses, but it's a start.