We're still closely monitoring the chances of a government shutdown. Check here for the latest updates. 

After Republicans passed a major tax rewrite on Wednesday, budget experts thought there was no way Congress would let the government shut down days later.

“It's hard for me to believe they'd step on their own story with a shutdown,” Stan Collender, a nonpartisan budget expert and columnist for Forbes, told The Fix in an email earlier this month.

But we can't entirely rule out a shutdown going into Congress's Christmas break. Lawmakers have until midnight Friday to pass a spending bill to keep the government open, and Republican leaders don't have a plan for how to do that.

A  bipartisan deal to pass a long-term spending bill disintegrated hours after Republicans' tax victory, and now they are scrambling to figure out how to pass short-term spending bill that kicks everything down the road to January.

“Ambiguity in the presence of a deadline is not Congress’s finest moment,” Molly Reynolds, a congressional expert with the Brookings Institution, said Wednesday.

By Thursday morning, Reynolds put the likelihood of a government shutdown at 5 to 10 percent. Collender was more pessimistic, putting the likelihood at 20 to 25 percent.

Here are the five likeliest scenarios that could still shut down the government, ranked.

5. House conservatives revolt

The House Freedom Caucus is often at the center of government shutdown threats. The 30 or so hard-line Republican lawmakers tend to vote against spending bills because the group believes they will raise the deficit. So they attempt to leverage their votes for policy victories, such as in 2015 when they tried to defund Planned Parenthood and the government came to the brink of a shutdown.

This week, Freedom Caucus members recoiled at tacking onto a spending bill a historically expensive $81 billion disaster aid package for communities struggling with hurricane and wildfire recovery.

Which brings us to our next point ...

4. Democrats refuse to support a short-term spending bill

To make up for the lack of House Freedom Caucus votes, Republicans have traditionally relied on Democrats to pass their spending bill.

But at the 11th hour, House Democrats have said: Don't count on us. They were hoping to use a vote on a long-term spending bill as an opportunity to protect dreamers, fund the expired children's health insurance program and get more disaster relief for Puerto Rico. Voting on a short-term spending bill gets them nothing.

If House Speaker Paul D. Ryan (R-Wis.) can't persuade Democrats to get on board with a short-term spending bill, he's got to figure out a way to get House conservatives on board, something he hasn't been able to do yet in his tenure as speaker.

3. Democrats go to the mat for dreamers

Democrats in the Senate and the House can still try to leverage their votes for policies on their agenda. No. 1 on that list: protections for young undocumented immigrants, also known as “dreamers,” that Trump recently rescinded. House Minority Leader Nancy Pelosi (D-Calif.) recently told reporters that Democrats “will not leave” Washington without a fix for Deferred Action for Childhood Arrivals.

But congressional Republican leaders have said they won't tackle immigration until next year, since dreamer protections don't officially expire until March. “This is something we’re going to turn to, I’m sure, in January,” said Sen. John Cornyn (R-Tex.) on Monday.

One way out of this impasse: Republicans could guarantee Democrats they'll address dreamers when Congress returns to work in 2018. (Congress can be very incremental that way.)

Maya MacGuineas, president of the bipartisan Committee for a Responsible Federal Budget, said Congress will probably find creative ways to get past these sticky issues: “There's no incentive or desire on either side to have a shutdown,” she told The Fix in an email, putting the shutdown threat at 0 percent.

2. Republican hawks revolt

This is a relatively new dynamic. A sizable number of pro-military House and Senate Republicans were hoping that Congress would pass a bill beefing up military spending by more than $650 billion, which is about $100 billion more than where it stands now.

But this last-minute short-term spending bill leaves defense spending at current levels for at least another month. That's unacceptable to these lawmakers. Politico reports many members of the House Armed Services Committee are threatening to vote against a short-term spending bill. Couple that with conservative House Republicans and frustrated House Democrats sitting on the sidelines, and GOP congressional leaders might not have enough votes to pass even a short-term spending bill that pauses this fight until January.

Steve Bell, a former GOP budget aide now with the Bipartisan Policy Institute, put the chance of a government shutdown this week at 20 percent thanks to this scenario.

1. Trump 

Not being able to predict Trump is Congress's biggest hurdle to getting anything done.

No one knows what he wants or who he'll side with, even after he makes his decision. In September, he sided with Democrats over a budget and debt ceiling showdown and agreed to discuss protecting dreamers. Then he flipped his position on immigration several times in one day.

It's also possible Trump just wants a shutdown fight. “The president has said a shutdown is possible at least three times now,” Bell of the Bipartisan Policy Institute said.

But for now, Trump seems to be in the mood to compromise so they can spend the holidays talking about their tax bill and not a shutdown.

I don't know exactly what the deal to get them there will look like, or just how much will get punted to January,”  Reynolds of Brookings said, “but I think, in the end, the prospect of shutting down the government at Christmas is bad enough that they'll find a way out.”