Romney was born in and grew up in Michigan, where his father served as a popular two-term governor. Pennsylvania has a large population of white, working-class voters, which has long been one of Obama's weakest demographic groups. A significant shift in momentum for Romney could put those and other states back in play.
Carl Forti, a top adviser to the Crossroads groups and Restore Our Future, another pro-Romney super PAC, said the battleground map "absolutely" could expand and that, if it does, the Republican-leaning groups will be eager to take advantage.
"For people who have only partially been paying attention until now, we have an opportunity to win them over," Forti said. "As long as they're disgruntled with the current president, they'll continue to look elsewhere."
Both sides are looking at Wisconsin as a potential new battleground after Romney named Wisconsin Rep. Paul Ryan as his running mate. Americans for Prosperity and Restore Our Future each spent about $2 million there earlier in the campaign after Republicans beat back a Democratic- and union-backed effort to recall GOP Gov. Scott Walker. Priorities USA Action has recently begun airing ads in Wisconsin, where polls still show Obama leading Romney.
Associated Press writers Jack Gillum in Washington and Jim Kuhnhenn in Portsmouth, N.H., contributed to this report.
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