Between the income tax expirations, the estate tax provision and a business investment provision that Democrats would limit to small businesses, the Democratic plan would raise almost $82 billion more in taxes in 2013 than the Republican version. But the Democrats’ claim to fiscal prudence may be undermined by their decision to maintain the stimulus law’s tax breaks, which would cut those savings down to $55 billion.

Republican tax aides say the vast majority of the benefits Democrats are seeking to preserve are not tax cuts but checks written by the Internal Revenue Service and sent to the working poor. Given the huge increase in government aid, like food stamps and unemployment benefits, letting some assistance lapse makes sense, they say.

N. Gregory Mankiw, a former Bush White House economic aide and an adviser to Mitt Romney, said that a typical family in the lowest 20 percent of the income scale now receives $3 in government benefits for every $1 earned. Even the middle 20 percent receives slightly more in government largess than it pays in taxes, he said.

[Mr. Mankiw subsequently noted on his blog that the data he used, from the Congressional Budget Office, includes state and local benefits as well as federal benefits, but reflects only federal taxes. He said correcting this inconsistency might change his conclusions, but that the CBO does not provide the data to know for sure.]

“What happened to the failed stimulus being ‘targeted, timely and temporary?’ ” asked Antonia Ferrier, a spokeswoman for Senate Finance Committee Republicans. “With our economy as weak as it is, stopping the president’s massive tax increase on nearly a million small businesses and then overhauling our burdensome tax code is how we’ll get America moving again. The same can’t be said for keeping the expanded stimulus spending through the tax code.”

At issue are four measures from the stimulus law. One reduced the eligibility threshold to $3,000 in earned income for the child tax credit. Without it, the threshold will jump to $13,300 next year, costing nearly nine million families about $7.6 billion, an average of $854 a family, according to the liberal group Citizens for Tax Justice. But the hit could be considerably larger. Currently, a family with one full-time minimum wage earner and two children receives a total child tax credit of $1,812, almost equal to the full $2,000 credit middle-income families with two children receive, said David Harris, president of the Children’s Research and Education Institute. If the stimulus provision lapses, that family’s credit would drop to $267, a $1,545 loss.

The stimulus also enlarged the earned income credit for families with three or more children, reduced the “marriage penalty” on working poor couples by starting the earned income credit phaseout at a higher level for married earners, and expanded the middle-class tax deduction for higher-education tuition. The 2009 American Opportunity Tax Credit expanded the tax break for tuition, fees and educational expenses to $2,500 from about $1,800, and doubled the length of eligibility to four years of school from two. It also made the first $1,000 of the tuition credit refundable, meaning that a family without enough federal income tax liability could get a check from the I.R.S. to offset higher education costs.

In all, the Republican plan would extend tax cuts for 2.7 million affluent families while allowing tax breaks to expire for 13 million on the bottom of the income spectrum, tax analysts say. An impact analysis released Monday by Congress’s Joint Committee on Taxation said a permanent extension of all the Bush-era tax cuts would cut taxes on households with more than $1 million of annual income by $74,505 next year. The Democratic proposal would cut taxes for those same households by $7,055.