Senate Majority Leader Mitch McConnell and other leading GOP senators have made clear that they don't want candidate Roy Moore in the Senate after he was accused of sexual assault and women said he had pursued sexual relationships with them while they were teenagers and he was in his 30s.
But a victory by Democrat Doug Jones in the December 12 special election in the deep red state would cost the GOP a vote it could badly need on tax reform, unless Congress passes the bill before Christmas -- a promise President Donald Trump made to a crowd of supporters in Missouri Wednesday afternoon.
Here's a look at when the winner of the Alabama Senate race will take office -- and the options Republicans have:
Yes. Voters can write in candidates -- but their votes will be counted only if they could swing the election's outcome.
The decision by retired Marine Col. Lee Busby to enter the race this week could pick up steam. And there's no deadline to launch a write-in candidacy, which means others could join him.
The state's "sore loser" law prevents losers of primary elections from running in the general election. But that doesn't apply to write-in votes -- which means, for example, that incumbent Sen. Luther Strange, who lost the GOP primary runoff to Moore, could campaign as a write-in candidate.
Alabama's Sen. Richard Shelby, who has voted early in the race, told reporters Monday that he did not vote for Moore but instead for "a distinguished Republican write-in."
The candidates are competing for a relatively small pool of voters.
"Our initial projections were around 25% but we have seen some voter exhaustion with the heavy involvement from national media and we have since lowered that projection to 20%," said John Bennett, a spokesman for the Alabama secretary of state's office.
When will the winner take office?
Likely in early January.
First, Alabama has to certify the results. Its 67 counties have until December 22 to report their results to the State Canvassing Board, which is made up of three Republicans: Gov. Kay Ivey, Secretary of State John Merrill and Attorney General Steve Marshall.
The earliest the state could certify a winner would be December 26, but the secretary of state's office does not expect the canvassing board to be able to do so until January 3, and it could be even later, delayed by slow canvassing by the counties and jam-packed holiday schedules between Christmas and New Year's Day. Once it does, that certification would be sent to Washington immediately. Once the winner is certified, the Senate would likely in swear that person quickly.
A delay of two or three weeks between Election Day and being seated in office is normal. Sen. Scott Brown, a Massachusetts Republican, waited 16 days from his election to his swearing-in. Sen. Cory Booker, a New Jersey Democrat, faced a 15-day wait when he was elected in 2013. And Sen. Ed Markey, a Massachusetts Democrat, waited 21 days between being elected to replace John Kerry and taking office in 2013.
What's all this mean for tax reform?
McConnell recently told reporters that "no matter who's elected, they won't be certified until December the 23rd" and that "we're pretty confident that the tax issue will be dealt with by the current members of the Senate."
Of course, legislative deadlines are often missed -- which means a Jones victory could leave Republicans one vote shorter, with their 52-48 majority winnowed to 51-49. That would leave even less room for GOP defections on tax reform.
What if Moore wins and the Senate kicks him out?
In the wake of the allegations that Moore pursued sexual relationships with teenage girls -- including a 14-year-old -- while in his 30s, some Senate Republicans -- including Cory Gardner of Colorado, the National Republican Senatorial Committee chairman -- said that if Moore wins, he should be expelled.
The Constitution allows a two-thirds majority of the Senate to vote to do that -- meaning at least 19 out of 52 Republicans would have to join all 48 Democrats.
Such a vote would likely occur after a Senate Ethics Committee investigation. And it'd be up to McConnell to call for a vote on Moore's expulsion.
It'd be an exceedingly rare circumstance: The last time the Senate expelled a member was 1862, when it booted Southern state senators for supporting the Confederacy. Senators facing ethics scandals since then have generally resigned, rather than forcing a vote.
If Moore were elected and then expelled, Alabama's governor would again appoint an interim replacement and call a special election. Moore could run again -- and win.