The proposal illustrates the lengths lawmakers are going to in an effort to include new federal revenues in a fix for the “fiscal cliff,” the reckoning in January that would come when all Bush-era tax cuts expire and automatic spending cuts to military and domestic programs kick in.

Virtually every Republican in Congress has taken the pledge, pushed by Grover Norquist’s Americans for Tax Reform, never to vote for a tax increase — a pledge both parties see as a serious impediment to a tax compromise. But if tax rates snap back to the levels of the Clinton presidency on Jan. 1, any legislation to reinstate some of those tax cuts — but not all of them — would be considered a tax cut.

“Many Republicans are starting to realize something important: On Jan. 1, if we haven’t gotten to a deal, Grover Norquist and his pledge are no longer relevant to this conversation,” Senator Patty Murray, Democrat of Washington, said this week in a speech at the Brookings Institution. “We will have a new fiscal and political reality.”

The idea inflamed passions on both sides on Tuesday, when fiscal issues careening toward Congress roiled hearings and deliberations and spurred political recriminations as Republican leaders accused Democrats of steering the economy back into recession .

“Democrats in Congress are now saying that they would rather see taxes go up on every American at the end of the year than let about a million businesses keep what they earn now,” Senator Mitch McConnell of Kentucky, the Republican leader, said Tuesday. “This isn’t an economic agenda. It’s an ideological crusade.”

Democrats accused Republicans of holding the vast majority of the Bush-era tax cuts hostage to the fraction aimed only at the rich. They praised the tough line adopted by the Democratic leadership, which is aligning with President Obama on the tax issue.

“This is all about leverage being on the side of the Democrats,” said Representative Peter Welch, Democrat of Vermont. “If Democrats want to use that leverage, we can’t blink.”

Lawmakers on both sides are now lamenting the fiscal train wreck that many of them voted to create, a confluence of spending cuts and tax increases that the Federal Reserve chairman, Ben S. Bernanke, said Tuesday could send the economy into recession.

At the same time, former Vice President Dick Cheney was meeting with Senate and House Republicans, in part to warn them of the dire consequences he sees in $500 billion in automatic military cuts that will begin to hit on Jan. 2. Off Capitol Hill, a broad bipartisan coalition of fiscal hawks, led by the co-chairman of President Obama’s 2010 fiscal commission, Erskine B. Bowles, restarted efforts to pressure Washington to reach a “grand bargain” on deficit reduction.

But taxes remain a chasm in the Capitol as Senator Harry Reid of Nevada, the majority leader, moved to force votes in the coming days on Democratic tax proposals.