WASHINGTON -- The Senate last night passed a $700 billion bill to stabilize the credit markets after sweetening an earlier version with tax credits and depositor protection to make it an easier sell to a House of Representatives that Monday rejected it.

Last night's 74-25 vote followed a week of mayhem on Wall Street, which reacted to the House's earlier rejection with a 778 point drop -- roughly $1 trillion in value -- followed by a succession of rises and falls as investors bailed then went bargain-hunting only to sell again.

In the House, leaders were working feverishly to convert enough opponents of the bill to push it through by tomorrow. Proponents needed to turn around at least 12 votes from that 228-205 defeat.

One of those on the fence is Rep. Tim Murphy, R-Upper St. Clair, who said last night he had not decided if the revisions made by the Senate were enough for him to change his vote.

He said he remained concerned whether that such a large government outlay would have the desired effect and that the marketers of the faulty securities would be held to account.

"I'm still concerned about the accountability issue," he said.

The bill passed by the Senate authorizes the Treasury to spend as much as $700 billion to buy bad mortgage-related securities and other devalued assets held by troubled financial institutions. If successful, advocates say, that would allow frozen credit to begin flowing again and keep the economy from a deep recession.

"It's a sad day that a government that's this strong and powerful and an economy that's been so powerful over so many generations has to do this," said Sen. Bob Casey, D-Pa., a member of the Senate Banking Committee.

He voted for the bill as did Sen. Arlen Specter, a Republican and Pennsylvania's senior senator.

"Listen -- we're elected to solve problems. We're going to dig in and get it done one way or the other. We cannot walk away from this," Mr. Specter said. "If we walk away from it totally and the market sees nothing in sight, the consequences are going to be cataclysmic."

Both parties' presidential candidates, Republican John McCain and Democrat Barack Obama, left the campaign trail to vote their support.

Senate leaders last night promised to promptly convene a series of hearings, likely in the banking committee, at which bankers and brokers who foisted faulty mortgages on the financial system would be called to book.

"Everybody's angry. Let's not kid ourselves. We're angry that we're here," said Sen John F. Kerry, D-Mass.. Mr. Kerry predicted that hearings could begin as early as this month.

House GOP opposition appeared to be easing after the Senate added $110 billion in tax breaks for businesses and the middle class, plus a provision to raise, from $100,000 to $250,000, the cap on federal deposit insurance. They were also cheering a decision Tuesday by the Securities and Exchange Commission to ease rules that force companies to devalue assets on their balance sheets to reflect the price they can get on the market.

House Republican leaders have told Senate leaders that they now believe they will be able to muster the votes needed to get the bill through the House and onto President Bush's desk.

Rep. Jason Altmire, D-McCandless, one of 114 House Democrats who voted against the bill on Monday, said he hadn't changed his view despite liking some of what the Senate added to the bill

"The reason I voted against it on Monday is that I had a problem with the underlying premise," a premise Mr. Altmire said did not change with last night's action. Mr. Altmire said earlier that his office had been flooded with complaints from constituents about Washington's willingness to help Wall Street and not help them.

The additions to the legislation came after a marathon bargaining session led by Senate banking committee chairman Sen. Christopher Dodd, D-Conn., who slumped, exhausted, at a front row desk as debate wound on last night.

The vote came after sundown, the end of the Jewish New Year, and spread across party lines both in support and opposition. Sen. Jim DeMint, a conservative Republican from South Carolina, voted against the bill, calling the credit collapse a result of the government meddling in the economy in the first place.

"I can only hope the House will defeat it so we can pursue better alternatives," Mr. DeMint said.

He was joined in his criticism by Sen. Bernard Sanders, an independent socialist from Vermont, who said the bill "fails to deal with the deregulation fervor" that he said had caused the problem.

Sen. Richard Shelby, who as a House member voted against the federal bailout of Chrysler 30 years ago, said the expanded coverage of bank deposits by the FDIC stretches an already overstretched agency, and said the federal purchase of troubled securities is risky.

Sen. Bill Nelson, D-Fla., complained that the bill does not effectively limit heads of failed investment houses from profiting on the collapse.

"Some CEOs who caused this crisis in the first place will benefit from this bailout and walk away with golden parachutes," he said.

Mr. Dodd, who was overseeing debate, rose to vehemently disagree with that characterization, saying sections of the bill specifically limit executive buyouts.

"For the first time in the history of the Congress we are going to deal with golden parachutes," Mr. Dodd said.

Congressional leaders cautioned that, aside from the likely psychological lift the vote could give to a nervous stock market, the effects of the investment package are not likely to be felt immediately.

Treasury officials must now figure out which investment packages to purchase and hold to keep their value.

Among critics of the bill was Mr. Casey's predecessor, Republican Rick Santorum, who expressed doubt about the government's suitability as a market stabilizer. He wanted to see a hybrid of both limited government purchase of the troubled investments, and a series of loan guarantees that would let the private market do the work.

"We're not going in there as Warren Buffett would to make money for the American public. We're going in there for a public policy purpose and profit is of a secondary or even tertiary nature. That's a big concern. That's a higher risk venture because we're paying more for something than the market would pay," Mr. Santorum said.

"Instead of trying to fix the deal they're just going to sweeten it with things other people need to buy the deal," he said.

The package was attached to a popular measure to require health plans for 51 or more employees to give equal treatment to mental health or addiction if they cover such illnesses.