WASHINGTON - Congressional liberals rebelled Wednesday against a must-pass spending bill that would keep the government open past midnight Thursday, complaining that it would roll back critical limits on Wall Street and sharply increase the influence of wealthy campaign donors.

Sen. Elizabeth Warren (D., Mass.), a popular figure on the left, led the insurrection with a speech on the Senate floor, calling the $1.01 trillion spending bill "the worst of government for the rich and powerful."

Warren urged House Democrats to withhold their support from the measure in a vote scheduled for Thursday. But the fear of shutting down federal agencies for the second time in just over a year appeared to weigh more heavily on Democratic leaders than liberal outrage.

House Minority Leader Nancy Pelosi (D., Calif.) and Whip Steny Hoyer (D., Md.) both expressed concerns about the measure but were not mobilizing their members to vote against it.

Meanwhile, White House press secretary Josh Earnest said that "it is certainly possible that the president could sign this piece of legislation," even though it would undo a pillar of the Dodd-Frank financial regulatory overhaul by freeing banks to more readily trade the exotic investments known as derivatives. The legislation ranks among the administration's biggest domestic achievements.

"I don't think the vast majority of Democrats or even Republicans are going to look too kindly on a Congress that's ready to go back and start doing the bidding of Wall Street interests again," Earnest said. But he later added: "We certainly don't want to see a government shutdown."

Republican leaders, for their part, predicted that the House would easily approve the sprawling spending bill and send it on to the Senate, which would face a midnight Thursday deadline. The measure provides funding through September for the Pentagon and dozens of other federal agencies and contains hundreds of individual policy instructions - from the ongoing ban on federal funding for abortion to a new prohibition on the legalization of marijuana in the District of Columbia.

The bill includes some good news for the White House, including fresh funding to battle the deadly outbreak of Ebola in West Africa and the rise of the Islamic State in Iraq and Syria. And it would do nothing to upend Obama's contentious executive action on immigration or his health-care law.

Overall, however, the measure reflects the GOP's strengthened hand in Washington as the party prepares to claim full control of Congress in January. The Department of Homeland Security, which enforces the nation's immigration laws, would be funded only through Feb. 27, when Republicans plan to revisit the agency's budget in hopes of curtailing Obama's immigration action.

Another controversial provision would permit a wealthy couple to give as much as $3.1 million to political parties, 10 times the current limit.

And the Wall Street provision marks a big win for Republicans who have long complained the Dodd-Frank regulations are burdensome. In a conference call with reporters, former Rep. Barney Frank, the Massachusetts Democrat who cowrote the act in the aftermath of the 2008 banking crisis, called it "an absolute outrage" and "a road map for the stealth unwinding of financial reform."

Under the 2010 Dodd-Frank overhaul, banks are prohibited from using taxpayer-insured depositor funds for particularly risky derivative transactions.

Also gaining attention is a measure that would for the first time allow the benefits of current retirees to be severely cut. It is set to be attached to the massive spending bill, part of an effort to save some of the nation's most distressed pension plans.

The rule would alter 40 years of federal law and could affect millions of workers, many of them part of a shrinking corps of middle-income employees in businesses such as trucking, construction and supermarkets.

If passed, the change would apply to multiemployer pensions, where a group of businesses in the same industry join forces with unions to provide pension coverage for employees. The plans cover 10 million U.S. workers.

Overall, there are about 1,400 multiemployer plans, many of which remain in good fiscal health and would be untouched by the deal. But several dozen have failed, and several other large ones are staggering toward insolvency.

As many as 200 multiemployer plans covering 1.5 million workers are in danger of running out of money over the next two decades. Half of those are thought to be in such bad shape that they could seek pension reductions for retirees in the near future.

But the measure in Congress is also outraging retirement security advocates, who argue that allowing cuts to plans paves the way to trims for other retirees later.

"After a lifetime of hard work to earn their pensions, retirees don't deserve to receive a bad deal, in which they have had no say, cut behind closed doors and excluding the very people who would be impacted the most," said Joyce Rogers, a senior vice president for AARP, the lobbying group for older Americans.