The Republican Party is split about whether Alabama's GOP Senate candidate Roy Moore should stay or go following accusations by four women who said he pursued romantic or sexual relationships with them when they were teenagers and he was in his 30s. The immediate future of their party rides on that dividing line.

Nearly all Senate Republicans who have spoken publicly about the allegations against Moore, including Senate Majority Leader Mitch McConnell (Ky.), said Moore should go “if” the allegations were proven true. (Which is almost impossible to do, notes The Fix's Aaron Blake.)

A few party elders see no reason to wait for more proof. Moore should go right now, said Sen. John McCain (R-Ariz.) and Mitt Romney, the GOP presidential nominees in 2008 and 2012:

When viewed through the lens of politics, why the two sides respond to the set of facts differently is simple: Those in the “if true” camp have much more on the line politically in the Alabama race than those in the unequivocal camp.

Senate Republicans are trying to pass a tax bill with a margin of error of just two “no” votes. The margin of error would shrink to one if a Democrat wins in Alabama. Already, at least three Senate Republicans have said they wouldn't support a tax bill that adds too much to the debt.

No tax bill means no legislative victory for Republicans' first year controlling Washington in a decade. No legislative victory for Republicans means their defeats in state and local elections Tuesday could repeat in next year's midterm congressional elections, when control of the House of Representatives could be in play if there's a big enough Democratic wave.

“Well, I think all of us realize that if we fail on taxes, that's the end of the Republican Party's governing majority in 2018,” Sen. Lindsey O. Graham (R-S.C.) told Fox News Radio earlier this month. This week, he bluntly warned that “financial contributions will stop” if Republicans can't get a tax bill done.

It could get worse for Senate Republicans if Moore heeds demands to drop out and they lose Alabama.

If Democrats pick up the once-unwinnable Alabama Senate seat, they suddenly have a path to taking back control of the Senate. Granted, it's not an easy path: They need to pick up three seats and hold 10 seats in states that went for Trump.

Democrats had only two realistic options to knock off Republicans, in Nevada and Arizona. Now, they might have three, which is just enough to put the Senate in play.

A RealClearPolitics average of polls before the allegations became public shows Moore with a six-point lead over attorney Doug Jones, far from the nearly 30-point margin of victory Trump won Alabama by. It's an open question what Alabama GOP voters, who have chosen Moore twice in statewide elections, will decide Dec. 12.

To sum up why Republicans haven't completely ditched Moore yet: tax reform, their campaign bank accounts and their majorities in Congress. Republicans' immediate future success doesn't entirely depend on this one Alabama seat, but a lot is riding on the party keeping it.

By contrast, the “Moore out now” camp has far less on the line. Romney isn't in public office right now, and he prided himself on being the voice of conscience for the party during the 2016 election.

Key moments from a speech in which former GOP presidential nominee Mitt Romney said Donald Trump "is playing the members of the American public for suckers" (Sarah Parnass/The Washington Post)

He might run for a Senate seat in Utah next year, but that's a state that is no fan of Trump and the kind of Trump-ism brashness that Moore represents. Utah voted for Trump in November, but by at least 20 points less than it did for previous Republican candidates. In fact, Romney arguably benefits politically by demanding Moore get out.

McCain, meanwhile, is one of Trump's most forceful critics — if not the most forceful. Unlike other Republicans, McCain never really warmed up to Trump after he beat Hillary Clinton. It makes sense McCain would ditch Moore when he's come under fire for sexual indiscretions that ultimately repelled McCain from Trump when the “Access Hollywood” tape broke.

Speaking of Trump, we've been here before, almost exactly a year ago: a Republican Party torn between supporting someone accused of sexual misconduct and supporting their own agenda.

And like the presidential election, the Republican Party can't decide what to do. Ultimately, Republicans in Washington don't want to have to equivocate when it comes to Moore. But just like in 2016, those who do feel like they don't have a choice.