Congressional Republicans want a blanket extension, arguing that any tax increase would inhibit efforts to create jobs and strengthen the economic recovery, and in particular create a burden on small business owners who file with the Internal Revenue Service as individuals.
In addition, Romney has proposed an additional 20 percent cut in tax rates, and simultaneously promised to rein in future deficits. He has not laid out a detailed package of spending cuts to achieve his objectives.
Obama relied on a report by the nonpartisan Tax Policy Center for his claim that middle-class taxes would rise by an average of $2,000 "if Gov. Romney wants to keep his word."
Romney's aides immediately circulated a detailed rebuttal that said the Tax Policy Center had ignored parts of the former governor's plan in its estimate, and in particular had omitted "growth effects" of a proposed cut in the corporate income tax rate.
In an attack on the organization's impartiality, Romney aides noted that one of the report's three authors is a former economic staffer to Obama.
Obama's aides countered quickly, saying the head of the Tax Policy Center is a former senior member of George W. Bush's economic team and that another report author worked for President George H.W. Bush's administration.
They also said Romney's campaign relied on the same organization's work in launching attacks on three rivals during this year's struggle for the Republican presidential nomination.
For his part, Romney made no public appearances Wednesday. After a weeklong trip to Britain, Israel and Poland to highly mixed reviews, he returns to active campaigning on Thursday. His immediate destination is Colorado, including a fundraiser in Aspen that several Republican governors are expected to attend.
He also plans a bus trip through Virginia, North Carolina and Florida in the coming days, placing additional emphasis on the same group of swing states that has received much of Obama's attention. He is expected to name a vice presidential running mate before the Republican National Convention, which opens on Aug. 27.
While Romney was in Boston, his campaign greeted Obama in Ohio with a television ad that attacked the auto industry bailout Obama continued for pushing some car dealers out of business and costing workers their jobs.
"I received a letter from General Motors. They were suspending my credit line. We had thirty-some employees that were out of work," former dealership owner says Al Zarzour says in the ad.
Ohio leads the nation in employment in the auto parts industry, and polls generally show the bailout — which Romney opposed — contributes to Obama's support in the state. It was not clear how often the commercial would run, but officials said it was airing only in the Cleveland area.
Espo reported from Washington. Associated Press writers Steve Peoples in Washington, Beth Fouhy in New York and Ann Sanner in Mansfield, Ohio, contributed to this report.
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