The gambit is certain to anger some conservative House Democrats, who object to tax cuts that are not offset with spending cuts. But Senate strategists assume it will gain more House votes than it will lose.
If so, Congress would be poised to pass landmark legislation giving the government billions of dollars to buy deeply discounted mortgage-backed securities that are choking off credit and roiling the markets.
The strategy is risky because some House members might see it as a high-handed move by senators. Senate passage of a bailout measure has seemed assured all along. The showdown is in the House, but now the Senate is trying to force the House's hand.
Sen. Charles Schumer, D-N.Y., called it "a brilliant move" that will "help pick up votes on both sides of the aisle."
House Speaker Nancy Pelosi's reaction was much cooler. "The Senate has made a decision about how to proceed and what can pass that body," the California Democrat said. "The Senate will vote tomorrow night, and the Congress will work its will."
The new approach, announced Tuesday night by Senate Majority Leader Harry Reid, D-Nev., and Minority Leader Mitch McConnell, R-Ky., would tack large and contentious tax measures to the bailout bill. Senate leaders figure the House will have to approve it because the tax cuts are too appealing to Republicans and the financial rescue plan will still seem essential to most Democrats.
The Senate approach uses big, game-changing amendments. House leaders earlier were considering the smallest possible tweaks to the bill in hopes of picking up 12 more votes.
The Senate bill would raise federal deposit insurance limits to $250,000 from $100,000, as called for presidential nominees Barack Obama and John McCain only hours earlier.
House Minority Leader John Boehner, R-Ohio, praised the move, but many Democrats had signaled approval as well.
McCain, Obama and Sen. Joe Biden of Delaware, the Democratic vice presidential nominee, signaled plans to return to Washington for the Wednesday night vote. If Obama and Biden vote for the measure, it would make it more difficult for Pelosi and other Democrats to reject or change the Senate measure.
The Senate measure will graft the bailout language to a tax bill it approved last week, on a 93-2 vote. It includes: a provision to prevent more than 20 million middle-class taxpayers from feeling the bite of the alternative minimum tax, $8 billion in tax relief for those hit by natural disasters in the Midwest, Texas and Louisiana and some $78 billion in renewable energy incentives and extensions of expiring tax breaks.
In a compromise worked out with Republicans, the bill does not pay for the AMT and disaster provisions but does have revenue offsets for part of the energy and extension measures.
That wasn't enough earlier this year for the House, which insisted that there be complete offsets for the energy and extension part of the package.
The Senate move seems aimed at forcing the House into accepting the deficit-financed tax cuts.
The surprise move capped a day in which supporters of the imperiled economic rescue fought to bring it back to life, courting reluctant lawmakers with a variety of other sweeteners including the plan to reassure Americans their bank deposits are safe.
Wall Street, at least, regained hope. The Dow Jones industrials rose 485 points, one day after a record 778-point plunge following the House vote.
Amid Tuesday's negotiations, Federal Deposit Insurance Corp. chairman Sheila Bair asked Congress for temporary authority to raise the limit on deposits by an unspecified amount. That could help ease a crisis of confidence in the banking system, Bair said.
She said the overwhelming majority of banks remain sound but an increase in the cap would help ease a crisis of confidence in the banking system as well as encourage banks to begin more lending.
Monday's House vote was a stinging setback to leaders of both parties and to Bush. The administration's proposal, still the heart of the legislation under consideration, would allow the government to buy bad mortgages and other deficient assets held by troubled financial institutions. If successful, advocates of the plan believe, that would help lift a major weight off the already sputtering national economy.
Bush renewed his efforts to save the bailout plan Tuesday, speaking with McCain and Obama and making another statement from the White House. "Congress must act," he declared.
Though stock prices rose, more attention was on credit markets. A key rate that banks charge each other shot higher, further evidence of a tightening of credit availability.
The rescue package was Topic A on the presidential campaign trail.
"The first thing I would do is say, 'Let's not call it a bailout. Let's call it a rescue,"' McCain told CNN. He said, "Americans are frightened right now" and political leaders must give them an immediate solution and a longer-term approach to the problem.
Obama issued a statement saying that significantly increasing federal deposit insurance would help small businesses and make the U.S. banking system more secure as well as restore public confidence.
Associated Press writers Tom Raum, Ben Feller, Alan Fram and Jim Kuhnhenn contributed to this report.