In Pennsylvania, a state judge in January blocked the state from asking voters to show a state-issued photo ID in the coming elections. The state’s photo ID law was passed in 2012 and is one of the strictest in the country. The judge said the requirement “unreasonably burdens the right to vote” for hundreds of thousands of people, many of them poor, disabled and older, and was not needed to prevent in-person voter fraud since none had been found in the state.

Pennsylvania’s Republican governor, Tom Corbett, who is locked in a tough re-election bid, decided in May not to appeal the ruling.

And in a significant decision in Wisconsin, a federal judge was the first in the country to rule that the state’s photo ID law was unconstitutional and violated Section 2 of the Voting Rights Act, which bars discrimination against minorities.

Last year, the Supreme Court weakened the Voting Rights Act, overturning a key section that helped protect voters in certain states, many of them in the South, from discrimination. The Department of Justice has brought lawsuits in Texas and North Carolina under the Section 2 provision, a new strategy more typically used to fight discrimination in redistricting cases.

The judge in Wisconsin found that the state presented scant evidence of voter fraud to justify the strict photo ID law, which had been blocked by a state court. Instead, the judge ruled, the law would disproportionately affect blacks, Hispanics and the poor since they are the least likely to have the required forms of government-issued identification, like a driver’s license or passport. The judge found that 300,000 registered voters in Wisconsin, roughly 9 percent, lacked the ID required to cast a ballot.

“The Wisconsin case is the most important of the voter ID cases that we’ve had,” said Nathaniel Persily, a Stanford University law professor and political scientist. “It’s a sophisticated analysis, it is extensive and it opens up a new area of inquiry on the Voting Rights Act.”

A state court judge in Arkansas also rejected as unconstitutional the photo ID requirements in May. But, in part because a primary was approaching, the judge allowed the state to move ahead with the requirement for now.