Obama won Ohio in 2008. Romney is expected to make a strong play for it in November.
Three days of in-person voting before Election Day were eliminated for most Ohio voters after a series of contentious election law changes cleared the state's Republican-controlled Legislature and Republican Gov. John Kasich signed them into law.
The Obama campaign has a network of people handling voter protection issues in states in a more informal way. For instance, the campaign has worked with state Democratic parties in Florida and Colorado to seek records in cases where the state claims to have a list to purge noncitizens from the rolls. But the campaign hasn't filed other lawsuits in state or federal courts.
"We don't resort to lawsuits as a matter of policy," said Bob Bauer, general counsel of Obama for America, the formal name for the president's re-election effort. Lawsuits are complicated, expensive, time-consuming and confusing, he added.
But Bauer said: "There isn't any other way to solve the problem in Ohio outside this federal court system. There's nothing we can do because the decision has been made, and that's how the state is preparing for the election."
Before the rollback, local boards of election had the discretion to set their own early, in-person voting hours on the three days before the election. People were allowed up until Monday before the Tuesday election to vote in person. Weekend voting varied among the state's 88 counties.
Whether the ability to vote during the final three days matters to Ohio voters remains unclear. People have other ways to vote, including casting an absentee by mail starting 35 days before the election and casting an in-person ballot on other days.
Norman Carmichael, 64, of Columbus, said he's taken advantage of the state's in-person voting rules before and he opposes any move that makes voting harder for people. "I don't think that's fair," he said, when asked about the restrictions on the three days before the election.
Rema Ina, 29, of Columbus, typically votes on Election Day and wasn't aware Ohioans could even cast a ballot in person before then.
"I'm not bothered by it because I didn't even know about it," she said.
Associated Press writer Calvin Woodward in Washington contributed to this report.
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