WASHINGTON (AP) — A hard-won, warts-and-all budget pact between House Speaker Nancy Pelosi and President Donald Trump is facing a key vote in the GOP-held Senate, with many conservatives torn between supporting the president and risking their political brand with an unpopular vote to add $2 trillion or more to the government's credit card.

The Trump-supported legislation backed by the Democratic speaker would stave off a government shutdown and protect budget gains for the Pentagon and popular domestic programs. It's attached to a must-do measure to lift the so-called debt limit to permit the government to borrow freely to pay its bills.

The vote, expected Wednesday afternoon or Thursday, is a politically tough one for many Republicans. The tea party-driven House GOP conference broke against it by a 2-1 ratio, but most pragmatists see the measure as preferable to an alternative fall landscape of high-wire deadlines and potential chaos. The government otherwise would face a potential debt default, an Oct. 1 shutdown deadline, and the return in January of across-the-board spending cuts known as sequestration.

Senate Majority Leader Mitch McConnell, R-Ky., is confident it will pass despite the misgivings of many Republicans.

But for new arrivals to the Senate, particularly those who ran against a broken Washington culture, the sweeping measure represents a lot of what they ran against: unrestrained borrowing and trillion-dollar deficits, fueled by a bipartisan thirst for new spending.

"This budget process, if we can even call it a process, put taxpayers at the mercy of a House Speaker who has no interest in prudent budgeting," said freshman Sen. Josh Hawley, R-Mo. "Our system is not supposed to work this way. When the entire federal budget depends on four or five people striking a deal among themselves, something is not right."

The budget and debt bill, however, is a top priority for McConnell, who set up the initial talks — taken over by Pelosi and Treasury Secretary Steven Mnuchin earlier this month — and pushed to isolate conservative forces in the White House who were disruptive. Top Senate Democrat Chuck Schumer of New York and House GOP leader Kevin McCarthy of California are also supporting the deal.

For House Republicans, as the minority party, it was easy to take a pass on voting for the legislation. Pelosi also made a point of showing she had enough Democratic votes to push it through without their help. But it's a different dynamic in the Senate, where Republicans hold the majority and are expected to deliver a strong vote for a Trump-backed agreement.

The agreement is a victory for pragmatists eager to avert chaos caused by a potential government shutdown, a possible debt crisis, or a freeze to agency budgets — including the massive Pentagon budget — at current levels. That would mean a continuing resolution, or CR, which could interfere with new weapons procurement and foster waste.

"The alternative's worse. It's either have a CR or another government shutdown and I think you have to believe this is the best you can do in divided government," said Sen. Rob Portman, R-Ohio. "You can't pull back. If you go to a CR for defense we'd be losing a lot of what we've gained on the defense buildup. So, you know, I don't love it but on balance it's better than the alternative."

Minority Whip Dick Durbin, D-Ill., said he expected a strong showing by the Senate's Democrats in favor of the bill. And GOP leadership stalwarts like Sens. Roy Blunt, R-Mo., Roger Wicker, R-Miss., and John Cornyn, R-Texas, swiftly swung behind the measure, calling it about the best result possible in a legislating matrix that demands Pelosi's blessing for bills to become law.

"So what price did we have to pay to get this? We had to give Nancy Pelosi a 4% increase this year in domestic spending and zero increase next year for an average annual increase that's less than the growth in (gross domestic product)," Wicker said, adding that many House Republicans took the "vote no, hope yes" approach to the legislation.

"I want to know what better deal anybody could have crafted that got Nancy Pelosi's sign-off in the House and Mitch McConnell's sign-off in the Senate, along with McCarthy and Schumer," Wicker said.

The agreement between the administration and Pelosi lifts the limit on the government's $22 trillion debt for two years and averts the risk of the Pentagon and domestic agencies from being hit with $125 billion in automatic spending cuts that are the last gasp of the 2011 Budget Control Act, a complex experiment aimed at forcing lawmakers into tough fiscal decisions that they couldn't arrive at on their own.