WASHINGTON — Is the government going to shut down Friday? A majority of lawmakers on both sides of the aisle are motivated not to let what would be the third shutdown this year happen.

They may not have a choice, though. We’re hours away from a midnight Friday deadline for Congress to appropriate money for a budget deal to which lawmakers agreed in February. Late Wednesday, lawmakers finally introduced a bill that would fund the government through Sept. 30, the end of the fiscal year.

There were last-minute holdups on big issues, like how much to fund President Donald Trump’s U.S.-Mexico border wall and whether to include gun-control provisions.

“The issues outstanding have large political constituencies,” Steve Bell, a former GOP budget analyst, said. “Without any immigration to really tempt Democrats, it will take some real dealing to get things done by Friday.”

Another option is that lawmakers run out of time and have to pass another short-term spending bill, their sixth of the year, to extend the funding deadline through the weekend.

“It could happen,” Sen. John Thune, R-S.D., told my colleague Erica Werner of the possibility of a shutdown or extending the deadline a few days.

If another stopgap measure or even government shutdown happens, here’s how things will probably go:

House conservatives revolt

There’s not a lot in this bill for conservatives to like. It boosts federal spending on domestic programs – a big Democratic get – and funds the Internal Revenue Service to help the agency enact Republicans’ new tax bill.

Expect 20 to 30 House conservatives to vote against the measure on the principle that it raises spending too much.

“I have not heard anything from any of my colleagues that would give me a whole lot of hope that there will be conservative wins,” House Freedom Caucus Chairman Mark Meadows, R-N.C., told my colleagues earlier this week.

That means House Speaker Paul D. Ryan, R-Wis., will have to rely on House Democrats to make up the difference and vote to fund the government. (The House vote will happen sometime Thursday, about 36 hours before the government could shut down.)

Democrats revolt on immigration

Another must-pass spending bill, another moment where Democrats find themselves with a sizable amount of leverage. And because this is likely to be the last must-pass piece of legislation before the November midterm elections (yes, really), Democrats are digging in on a few campaign issues.

Some of their demands, most of which got met in the final bill:

President Trump can have $1.6 billion for his border wall but not hundreds of new immigration agents to patrol the border. After some hesitation, Trump seems to have agreed to this.

Actually, they want most of that money to go toward repairing existing barriers or technological eyes in the sky and not for concrete barriers like the ones Trump has proposed. Trump seems to reluctantly have agreed to this, too.

They want some kind of gun-control measure in the bill. And it looks like they got it: Republicans agreed to allow federal funds to be spent on research for gun violence.

They want a vote on protecting undocumented immigrants known as “dreamers” from deportation. (A deal on that is looking less and less likely.) On Thursday, House Minority Leader Nancy Pelosi, D-Calif., sent a letter to Democrats urging them to vote against the spending bill because House Speaker Paul D. Ryan, R-Wis., hasn’t yet allowed a vote to protect dreamers. It’s unclear how many Democrats could follow her lead, but if enough do, it could derail the entire spending bill.

One or two senators revolt over niche issues

While most of us were sleeping on the night of Feb. 8, the government shut down for a few hours after Sen. Rand Paul, R-Ky., seized the Senate floor, trying to force senators to vote on an amendment that basically says they failed to rein in federal spending when they passed their tax bill.

Paul isn’t ruling out doing something like that again. He’s the likeliest candidate to hold up this spending package, but there are others.

One senator who’s likely to be particularly upset with this deal is Sen. Susan Collins, R-Maine. She traded her reluctant vote in favor of December’s tax bill for a future vote to shore up Affordable Care Act subsidies. Except Republican leaders haven’t held up their end of the bargain, and it looks as though the House will vote on a bill that lacks health-care provisions. That means Collins may have lost her chance. But a filibuster from the normally congenial senator would be a big surprise.

And Senate Minority Leader Charles E. Schumer, D-N.Y., is frustrated by the White House’s attempts to block about $900 million in federal funding for a crucial tunnel linking New York City and New Jersey, although he seems to have accepted the White House won that one. Supporters of the Gateway project say they can get taxpayer funds elsewhere.

Speaking of the White House, here’s our final hurdle to a shutdown. And it’s the most unpredictable of all:

Trump revolts

He’s getting some money for his border wall, but it’s a fraction of the $25 billion he wants.

Trump tweeted “Democrats refused to take care of DACA. Would have been so easy, but they just didn’t care. I had to fight for Military and start of Wall.”

The spending bill is also likely to give the FBI hundreds of millions to combat Russian hacking, which is entirely incompatible with the president’s stance that people in the FBI are out to get him.

Trump tweeted “Andrew McCabe FIRED, a great day for the hard working men and women of the FBI – A great day for Democracy. Sanctimonious James Comey was his boss and made McCabe look like a choirboy. He knew all about the lies and corruption going on at the highest levels of the FBI!”

Plus, Trump has mused in the past that shutdowns could be “good,” both for the nation and for him politically.

“If a shutdown happens,” said budget analyst and Forbes columnist Stan Collender, “it will only be because Trump wants it.”

It seems like the present indeed hesitated for a moment Wednesday on accepting on the deal. But he appears to have come around to supporting it, which neutralizes the final hurdle to a shutdown.

Trump tweeted “Got $1.6 Billion to start Wall on Southern Border, rest will be forthcoming. Most importantly, got $700 Billion to rebuild our Military, $716 Billion next year…most ever. Had to waste money on Dem giveaways in order to take care of military pay increase and new equipment.”