Democrats want Doug Jones seated right away. The GOP wants to finish a tax overhaul.

It will most likely take a few weeks for Jones to be sworn into the Senate.

Doug Jones just scored a stunning victory as a Democrat in Alabama’s Senate race. The next big question is when he will take his seat in the Senate.

The timing matters because Jones’s victory narrows the Republican majority in the Senate to a tenuous 51 votes. Congressional Republicans are about to vote on a sweeping overhaul of the tax system that would slash taxes for corporations permanently, for individuals temporarily, and add more than $1 trillion to the national debt over the next decade.

But if Congress votes on the bill next week, it’s likely Jones won’t yet be there to vote for it. The timeline indicates Jones should be sworn in early January at the earliest — but there are still a couple of potential roadblocks.

It takes some time to officially certify the election results: Counties must officially file their election results by Friday, December 22, according to the Alabama Secretary of State’s office. John Bennett, chief of staff for the Alabama secretary of state, told Reuters that some counties might miss that deadline, which would mean December 26 would be the earliest for the final results to be certified.

The latest the results could be certified is January 3.

After that, it depends on the Senate. Congress is likely to be in recess until after the New Year. Sen. Majority Mitch McConnell’s office told Time that Jones’s swearing-in date hasn’t been set.

Democrats want Jones to be seated right away. Republicans want to finish tax reform.

Right now, the Republicans’ biggest legislative priority is getting their tax bill passed. They had promised to deliver it to President Trump before the end of the year. The House and Senate have reportedly reached a final agreement — but it’s not clear if all of GOP senators who voted for it initially are still on board. Jones’s victory could potentially upend that plan if the party can’t reach a final deal by the time he becomes a senator.

As Vox’s Dylan Scott writes, the Republicans passed the bill with 51 Republican votes. Sen. Bob Corker (R-TN) defected — the only Republican to do so. But Sen. Susan Collins (R-ME) is beginning to push back, which would drop the vote count down to 50. Without Jones, Republicans can still pass the bill — Vice President Mike Pence will break the tie. But if Jones shows up in time:

This path to failure has become clear: Jones wins in Alabama on Tuesday, the tax negotiations drag on long enough for him to be seated, and Collins flips to a “no” vote because her extracted concessions on health care fall through.with their current numbers.

As Scott points out, this is the best-case scenario for Democrats. But Republicans also can do the math, and will push hard to deliver the tax bill before Jones arrives.

So far, McConnell hasn’t indicated that he’d delay seating Jones. But Senate Democrats are clearly worried that he will, and are pushing for Jones to be seated as soon as possible:

A similar debate played out in 2010, after Republican Scott Brown won a surprise victory in the Massachusetts Senate special election and deprived Democrats of a 60-vote, filibuster-proof majority in the Senate.

One option for Democrats was to push the health care bill through before Brown was seated. But then-Senate Majority Leader Harry Reid said the day after the election that they wouldn’t act on health care until Brown was sworn in.

So far, McConnell has made no such assurance on the tax bill.

Moore hasn’t conceded yet. What does that mean?

On Tuesday night, after Jones’s victory speech, Republican Roy Moore refused to concede, saying “when the vote is this close that it's not over” and calling for a recount. Typically, a campaign demanding a recount also pushes to delay the swearing-in until after the recount is finished, which could hold up Jones being seated.

Recounts can only happen after the election results have been certified, according to AL.com, so the recount wouldn’t delay certification.

Besides, the vote is close, but not that close. Alabama law provides for an automatic recount if the vote differential is a half percentage point or less. Jones won by more than 20,000, putting his estimated margin of victory at 1.5 percent. The Alabama Secretary of State John Merrill said any candidate can request a recount — though they’ll have to foot the bill if it exceeds the half percent.

It’s not entirely clear, though, if the Alabama law even applies to candidates for federal office, as Rick Hasen writes at the Election Law Blog. And Merrill told CNN that it’s “highly unlikely” that the outcome of the vote will change. “There's not a whole lot of mistakes that are made,” he said.