The top issue among voters remains the struggling economy and 8.2 percent unemployment, but Obama has managed through recent attacks on Romney’s business record to distract him from his message. Romney wants to focus on Obama’s economic policies — that Republicans say have failed.

Obama is in Texas on Tuesday, hoping to raise at least $4 million from gay, Latino and big-dollar donors. Romney is campaigning in Pennsylvania, one of the 10 or so states that likely will determine the outcome of the election. Florida is another, and the Obama campaign said Tuesday that the president would make a two-day campaign swing there Thursday and Friday.

Romney supporter and former New Hampshire governor John H. Sununu had to explain himself Tuesday when he criticized Obama’s economic policies and said the president needed to “learn how to be an American” on a conference call with reporters organized by Romney’s campaign. Later in the call, he was asked to clarify his comments. “The president has to learn the American formula for creating business,” Sununu said.

The comments evoked the claims of the so-called birther movement, which accuses Obama of not being a natural-born U.S. citizen, and therefore being ineligible to be president — claims that have been repeatedly debunked.

In Texas, Obama faces a state that has not voted Democratic in a presidential contest since 1976. But Texas ranks among the states with the largest concentrations of wealth, along with New York, California, Florida and Illinois.

The Obama camp also was airing an ad taking issue with Romney’s decision to release only two years of his personal tax returns. The ad questions whether Romney has avoided paying his share of taxes in certain years.

Romney has released his 2010 tax return and has said he will release his 2011 return. He has said he will not release other returns, breaking with the custom of past candidates dating to his father, George Romney. He set the standard a generation ago by releasing tax returns for 12 years.

The Obama ad was running for one day only, a sign it was designed to drive media coverage.

The Obama campaign has hammered at Romney’s business record, especially discrepancies over when he departed as chief of the private equity firm Bain Capital that he co-founded in the 1980s. Romney says his business record is his chief qualification to be president, and it is the source of his vast fortune, estimated at a quarter of a billion dollars.

Meanwhile, a top Romney aide floated the possibility Monday that the candidate may name his vice presidential selection by week’s end, raising the level of intrigue around what may be Romney’s most significant decision before Election Day. But the timing was not certain.

Romney senior adviser Eric Fehrnstrom later downplayed the remark, suggesting the decision could come any time between now and the Republican National Convention at the end of August.

Obama continues to try to undermine public support in Romney’s business credentials and trustworthiness. In an interview, Obama defended his targeting of Romney and Bain, saying the public should know if some companies taken over by Bain at any time sent jobs overseas.

“That is hardly a personal attack. That goes to the rationale for his candidacy,” Obama said in an interview with WEWS-TV in Cleveland that aired Tuesday morning.

Romney has said he left Bain in early 1999, shortly before it invested in companies that were pioneers of job outsourcing. Romney says he played no role in those transactions and decisions.

Two years later, however, Bain was still filing disclosure documents with the Securities and Exchange Commission that named Romney as the firm’s CEO, president, sole shareholder and “the controlling person.” At least one document in early 2001 said Romney’s “principal occupation” was as Bain’s managing director.

Bain says it took some time for disclosure forms to catch up with management changes at the firm. Romney says he was working full-time on the 2002 Salt Lake City Winter Olympic Games starting in early 1999.

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Associated Press writers Jim Kuhnhenn, Steve Peoples and Charles Babington contributed to this report.