As the House began to take up the tax deal, it hit a procedural snag. Liberal Democrats skirmished with party leaders over a proposed vote on an amendment to tax more wealthy estates and at a higher rate than was included in a provision agreed to by the Obama administration.
The liberals, many of them angry about the prospect of continuing the tax policies of President George W. Bush, complained that party leaders had structured the debate so that they could not vote in favor of the amendment to the estate tax provision without also voting in favor of the entire package.
Representative Charles B. Rangel, Democrat of New York, said he supported the change in the estate tax, which he said would save $23 billion. But, he complained, ?in order to do that I would have to accept the remainder of the Senate bill.?
By Thursday evening, however, an accommodation had been reached and floor action resumed. In a key test, the House voted 214 to 201 to approve the new terms of debate.
The bill extends for two years all of the income tax cuts enacted under Mr. Bush and provides a one-year payroll tax cut for most American workers, delivering what economists predict would be a needed lift for the struggling economy.
The tax deal marked the start of a new dynamic in Washington, with Republicans set to hold a majority in the House as result of their big victories in the midterm elections.
The package was negotiated directly by Vice President Joseph R. Biden Jr. and the Senate Republican leader, Mitch McConnell of Kentucky, who has positioned himself as a broker between the White House and Republicans.
Some officials, including Mr. Obama, have hailed the tax agreement as a prototype for hard-bargained compromises in the era of divided government.
But the tax accord also showed Washington policymakers locked in an unsustainable cycle of cutting taxes and raising spending that has proved politically palatable in the short term but could seriously threaten the nation?s fiscal stability in years ahead.
?Republicans are talking a lot about certainty and there is some good data about this, that policy uncertainty is bad for an economy,? said Matthew Mitchell, a research fellow and tax policy expert at George Mason University in Virginia.
?But even if they had won some sort of a victory where they got the current tax rates written in stone,? he said, ?spending is on such an unsustainable path in terms of entitlements, it really isn?t certain at all.?
The temporary nature of the deal, however, could lend momentum to broader efforts to overhaul the tax code and tackle the long-term deficit. With the tax debate now scheduled to resume at the height of the 2012 presidential election, some lawmakers say they hope the fiscal landscape can be redrawn and the cycle of lower taxes and higher spending brought to a halt.
Or, as Herbert Stein, the chairman of the Council of Economic Advisers under Presidents Richard M. Nixon and Gerald R. Ford put it: ?If something cannot go on forever, it will stop.?
Some fiscal experts said they were heartened that lawmakers in both parties had expressed unhappiness with the tax agreement, and that there appeared to be an increasing recognition of a need to tackle the long-term problems.
Recently, 22 senators ? 12 Democrats, 9 Republicans and 1 independent ? signed on to a resolution pledging to ?devise a comprehensive plan for addressing the fiscal concerns of our nation? by focusing on ?tax reform, spending restraint and debt and deficit reduction? in 2011.
?The era of deficit denial is over,? said Bruce Reed, the executive director of Mr. Obama?s bipartisan commission on reducing the national debt. ?They?re just having a big year-end close-out.?
Senator Tom Coburn, Republican of Oklahoma, for example, voted in favor of the debt commission?s plan earlier this month. But he voted against the tax deal on Wednesday even as his colleagues approved it overwhelmingly by a vote of 81 to 19. Mr. Coburn had proposed an alternative seeking to reduce the cost of the tax plan.
As the House debated the tax plan, some Democrats said it would do too much for the wealthy, and warned that the payroll tax cut could undermine the stability of Social Security. Some Republican critics said the package was too costly.
?This legislation creates too few jobs and too much debt,? said Representative Peter Welch, Democrat of Vermont.
Representative Jerrold Nadler, Democrat of New York, said he feared the one-year cut in the Social Security payroll tax, to 4.2 percent from 6.2 percent on income up to $106,800, would weaken Social Security because Republicans would insist on the cut being made permanent, and Democrats would relent.
?We know that, politically, once you make that tax cut it will be impossible to restore it,? Mr. Nadler said.
In the Senate, Democrats on Thursday night abandoned efforts to pass a $1.2 trillion spending bill to finance the federal government through Sept. 30, and said they would accede to Republicans demands for a short-term stop-gap measure instead.
Senators said the stop-gap bill would run through the early part of next year. At that point, Republicans will control a majority in the House and six additional seats in the Senate, giving them greater leverage over any spending decisions.