Limiting Tax Deductions May Work, but Not Easily Stephen Crowley/The New York Times Speaker John A. Boehner, shown on Tuesday, has made a deficit-cutting counteroffer that includes $800 billion in revenues. WASHINGTON - Behind President Obama's insistence that tax rates must rise on higher incomes is a belief that Republicans cannot raise as much revenue as they claim, $800 billion in the first decade, simply by limiting deductions and loopholes. Yet in the past, Mr. Obama supported that option to collect even more. Republican Congressional leaders, for their part, say it would be simple to design a plan limiting tax breaks for the affluent as part of a bipartisan budget deal. Yet they are not proposing how to do so because, well, it is not so simple. And it would certainly be controversial. On Tuesday, a day after Speaker John A. Boehner made his deficit-cutting counteroffer to Mr. Obama that included a proposal for $800 billion in revenues, his office provided no details about how to raise that money. Instead, Republican aides cited a nine-page paper last month from the Committee for a Responsible Federal Budget, a centrist business-supported group dedicated to lower deficits, with three options for limiting deductions as an alternative to letting the top tax rates increase. According to the analysis, each option could allow the government to collect about as much new revenue as it would if the top Bush-era tax rates of 33 percent and 35 percent expire as scheduled on Dec. 31 and revert to the Clinton-era levels of 36 percent and 39.6 percent, respectively, for couples with income above $250,000 and singles above $200,000. Mr. Obama has vowed since his first campaign to let the top Bush rates expire, though he extended them for two years after 2010 in a compromise with Republicans for stimulus measures. Mr. Obama is now standing his ground. He continued on Tuesday to insist that simple math argued that Republicans" alternative to higher rates would not work, not without affecting middle-income taxpayers and eroding charitable contributions from people seeking the tax advantages for their donations. "The only way to do that would be if you completely eliminated, for example, charitable deductions," Mr. Obama said in an interview on Tuesday with Bloomberg TV. Well, if you eliminated charitable deductions, that means every hospital and university and not-for-profit agency across the country would suddenly find themselves on the verge of collapse. So that's not a realistic option. The president restated his bottom line for the negotiations with Congress to avert a fiscal crisis in January: "What I'm going to need, what the country needs, what the business community needs in order to get to where we need to be, is an acknowledgment that folks like me can afford to pay a little bit higher rate." But since 2010, Mr. Obama and lawmakers in both parties have promoted - and oversold, in the minds of some experts - the idea that Washington could overhaul the tax code, strip out deductions, tax credits, exemptions and loopholes and use the resulting revenues to both lower tax rates and reduce annual budget deficits. That idea was the core of recommendations from the bipartisan Simpson-Bowles fiscal commission in 2010 that Mr. Obama created, and cleared the way for a majority of liberals and conservatives to agree. Months later, when Mr. Obama was engaged in ultimately unsuccessful negotiations with Mr. Boehner on a debt-reduction deal in the summer of 2011, he recounted his pitch to Republicans for reporters: "What we said was, give us $1.2 trillion in additional revenues, which could be accomplished without hiking taxes - tax rates - but could simply be accomplished by eliminating loopholes, eliminating some deductions and engaging in a tax reform process that could have lowered rates generally while broadening the base." Now, with time running out for a budget deal that would head off the automatic tax increases and across-the-board spending cuts scheduled to occur in January, some Democrats and Republicans predict a compromise that combines a higher top rate and reduced tax breaks for upper-income Americans. Mr. Obama has called for tax increases on the wealthy that would raise about $1.6 trillion more in the first decade, or twice the Republicans" offer. About $1 trillion would result from not extending the top Bush rates, the rest by limiting deductions but with a different approach than Republicans have offered.