Democrats said they saw that as a sign of weakness. Pointing to a Gallup poll from last week that indicated 60 percent of Americans supported the proposal, including 63 percent of political independents, Senator Charles E. Schumer, Democrat of New York, called the Republican response “proof positive” that “for first time in decades, maybe generations, they’re on the defensive on their signature issue,” taxes.

After he made that comment, a CNN poll was released putting support at 72 percent, including 53 percent of Republicans.

With taxes due on Tuesday, a Washington debate on the tax code this week was inevitable, but the escalating attacks reflect the peculiarities of this election year. Democrats have known for weeks that the Buffett Rule would not win the 60 votes needed to break a Republican filibuster, but they pressed forward in part to try to make the Republicans’ likely presidential nominee, Mitt Romney, the face of economic “unfairness.”

Mr. Romney paid an effective tax rate of 13.9 percent on $21.7 million in income in 2010, the only full year’s tax returns he has released. The Obama re-election campaign and the Democratic National Committee again pressed Mr. Romney on Monday to release more than a decade’s worth of tax returns, something his campaign has refused to do.

Photo

“I don’t think he’s going to want this present inequity to remain when he is a prime example of it,” Mr. Schumer said.

In the Senate, all the Republicans but Senator Susan Collins of Maine voted against allowing debate on the Buffett Rule. Every Democrat but Senator Mark Pryor of Arkansas voted to allow it. Four senators did not vote.

Republicans relished a debate on their turf, accusing Democrats of trying to raise taxes on investments and capital to feed their appetite for government spending. They portrayed the Buffett Rule as a gimmick and political show vote, whose revenue impact would not even dent the trillion dollar budget deficit.

Newsletter Sign Up Continue reading the main story Please verify you're not a robot by clicking the box. Invalid email address. Please re-enter. You must select a newsletter to subscribe to. Sign Up You will receive emails containing news content , updates and promotions from The New York Times. You may opt-out at any time. You agree to receive occasional updates and special offers for The New York Times's products and services. Thank you for subscribing. An error has occurred. Please try again later. View all New York Times newsletters.

Instead, the House will vote on a bill by Representative Eric Cantor of Virginia, the majority leader, to give businesses with fewer than 500 employees a 20 percent tax cut this year. Mr. Cantor says that while the Buffett Rule would raise taxes on “job creators,” his bill would spur job growth by easing the tax burden on small businesses.

Advertisement Continue reading the main story

Republicans and Democrats have created mirror-image arguments to take into the election year. The Cantor bill would cost the Treasury $46 billion. The Senate Democratic bill would raise $47 billion over 10 years — but $160 billion if the Bush era tax cuts for the affluent are extended.

Democrats argued for more fairness in the tax code. Their legislation would establish a 30-percent floor for households earning $1 million a year.

A White House statement on Monday supporting the Senate bill said “one in four taxpayers with annual income greater than $1 million today pays a lower tax rate than millions of hardworking middle-class households.”

Republicans argued that no one’s taxes should be raised while the economy is struggling to regain its footing. The House bill would offer a tax cut to small businesses, but it is drawn so broadly that it would benefit anyone with income through partnerships and other “pass-through” entities.” Almost half the benefit would accrue to the households with income over $1 million, according to the non-partisan Tax Policy Center.

The Democratic Senatorial Campaign Committee immediately went after the two most vulnerable Senate Republicans running for re-election this year, Scott P. Brown of Massachusetts and Dean Heller of Nevada, accusing them of standing by billionaires while their party tries to cut Medicare. And they vowed the measure would continue to come up this year.

“Sometimes special interests can take a punch or two, and it’s only the threat of public persistence that can move an issue along,” said Senator Sheldon Whitehouse, Democrat of Rhode Island, the author of the legislation.

But Republicans were just as much on offense. The National Republican Congressional Committee said vulnerable House Democrats could “either focus on growing small businesses by providing them tax relief to create jobs or help his party leaders raise taxes to fuel their spending addictions.”