This post has been updated as more GOP lawmakers bail from Trump ahead of Sunday's debate.

Even before the world heard Donald Trump make hard-to-hear comments about what he'd like to do to women, Republicans sharing the ballot with him were facing a tough decision: Do they cut and run from their presidential nominee, a move that could alienate their base of Trump supporters across the country? Or do they stick with their nominee and risk going down with him?

It's high-stakes game theory, and Republicans are coming up on decision day. If they want to get out of Trump's shadow, history suggests the last few weeks before Election Day — i.e., right now — is the time to do it.

Republicans will probably be watching two things closely as they mull over their options:

  1. The ongoing fallout from 2005 audio The Washington Post's David Fahrenthold published Friday of Trump making lewd comments about women. By Saturday afternoon, more than two dozen lawmakers decided to jump ship, including at least four vulnerable Senate Republicans.
  2. How Trump performs Sunday in the second presidential debate, which is likely his last chance to redeem himself with the party, and what the polls say in the days afterward.

If Trump isn't able to redeem himself Sunday, we could envision a world (and have!) in which vulnerable Republicans decide dealing with Trump and his baggage just isn't worth it anymore. They drop him, symbolically if not actually (more on how that works, below).

It's a risky decision. Rep. Joe Heck (R-Nev.) got booed Saturday when he announced he wouldn't be voting for Trump. Plus, there's no guarantee that ditching Trump now would help Republicans win over female and independent voters, who have been turned off to Trump for some time now.

But Republicans don't have a lot of time to mull over the consequences. Most observers think the time for the party to drop their nominee would be in the days after Sunday's debate, if polling shows Trump's performance and latest controversy give Hillary Clinton an even bigger boost than she's already enjoying.

“This election could end Sunday,” said John Hudak, a governance expert at Brookings Institution, who spoke to The Fix before news broke of Trump's lewd comments.

If Republicans wake up Monday morning and decide it's time to ditch Trump, here's how it would work:

At this point, dumping him would probably be a symbolic break rather than a financial or procedural one. Republicans are stuck with Trump on the ballot unless Trump himself decides to step aside. ("Never," Trump told The Post's Robert Costa on that last point.)

Before Friday's news, the Republican National Committee was still helping Trump with fundraising, ads, staff — basically propping up the most critical aspects of his campaign. There's no evidence it's going to pull the plug on that altogether. (Though if it did, here's what that would look like.)

The more likely scenario would be that congressional Republicans make clear to voters they've changed their minds and are no longer going to vote for Trump. It's a testament to just how damaging Republicans think the 2005 leaked audio of Trump is that some are pulling the rip cord before Sunday's debate. For the most part, GOP lawmakers in swing districts or vulnerable races are leading the way on that. House Speaker Paul D. Ryan (R-Wis.) and Senate Majority Leader Mitch McConnell (R-Ky.) have not rescinded their support for Trump. (Ryan did boot Trump from their first planned public campaign event Saturday in Wisconsin.)

There's a reason GOP leaders have so far proceeded with caution. If Republicans take any bigger steps back from their nominee, it could backfire on them — unless Trump's base is willing to walk away, too.

As we broke down in August, for a Trump-GOP divorce to go over smoothly, it would have to be the cleanest of clean breaks: Ideally, it would be so obvious after Sunday's debate that Trump is going to lose the presidential election that not even his biggest supporters would complain much about the Republican elite turning their backs on him.

Before Friday's news broke, Trump wasn't totally bombing in the polls, even after his rough performance in the first presidential debate. He was behind Clinton by an average five-point margin — enough for him to lose, but not necessarily drag down Hill Republicans with him. (No one really knows what the magic line is that would cause Hill Republicans to lose alongside Trump, but most observers say it's in the 10 to 12 percent range.)

Trump's standing in the polls could change with Friday's news. But Republicans don't have much more wait-and-see time left.

Back in 1996,  Republicans effectively dropped nominee Bob Dole two weeks before the presidential election by campaigning instead on not being a "blank check" for then-President Bill Clinton. It worked; they held onto their majorities in Congress while Clinton won reelection. But Dole and his supporters went quietly.

It's very hard to envision a world where Trump and his supporters do the same, even after Friday's bombshell.

For some Republicans trying to avoid a loss next month — and agonizing over their final Trump decision — this weekend is shaping up to be a no-win scenario.