HARRISBURG, Pa. — A judge has ruled that Pennsylvania voters won’t have to show photo identification to cast ballots on Election Day, a move that could help President Barack Obama in a presidential battleground state.

Commonwealth Court Judge Robert Simpson on Tuesday delayed Pennsylvania’s controversial voter ID requirement from taking effect this election, saying he wasn’t sure the state had made it possible for voters to easily get IDs before Nov. 6.

“I am still not convinced ... that there will be no voter disenfranchisement” if the law took effect immediately, Simpson wrote.

Gov. Tom Corbett, who had championed the law, said he was leaning against an appeal of the decision, which was widely viewed to favor Obama in Pennsylvania, one of the nation’s biggest electoral college prizes. Obama has been leading in recent polls over Republican nominee Mitt Romney.

The law could still take full effect next year, although Simpson could also decide to issue a permanent injunction.

The 6-month-old law, among the nation’s toughest, sparked a divisive debate in Pennsylvania over voting rights ahead of the presidential election. Voter ID laws have been toughened in about a dozen primarily Republican-controlled states since the 2008 presidential election. But states with the toughest rules going into effect — including Kansas and Tennessee — aren’t battleground states, making their impact on the presidential election unclear.

Opponents of the Pennsylvania law had said young adults, minorities, the elderly, poor and disabled would find it harder to cast ballots. One civil rights lawyer said the judge’s decision cemented the principle that a photo ID law can’t disenfranchise such voters.

“The effect of the decision in Pennsylvania is not just theoretically, can voters get ID, but actually, can they get ID,” said Jon M. Greenbaum, chief counsel of The Lawyers’ Committee for Civil Rights Under Law.

Simpson — a Republican first elected to the bench in 2001 — based his decision on guidelines given to him two weeks ago by the state Supreme Court to determine whether the state had made photo IDs easily accessible.

He ruled after listening to two days of testimony about the state’s efforts to ease requirements, as well as accounts of long lines and ill-informed clerks at driver’s license centers.

On Nov. 6, election workers will still be allowed to ask voters for a valid photo ID, but people without it can use a regular voting machine in the polling place and will not have to cast a provisional ballot or prove their identity to election officials afterward, the judge ruled.

“This decision is a big win for voters in Pennsylvania,” said Witold J. Walczak of the American Civil Liberties Union of Pennsylvania, which helped challenge the law.

The plaintiffs included the Homeless Advocacy Project, the League of Women Voters of Pennsylvania and the Pennsylvania chapter of the National Association for the Advancement of Colored People.

Corbett, a Republican, said he still believed that his administration would have made it possible for every registered voter who needed a valid photo ID card to get one.

Election law and voting rights scholars say voter ID requirements stop some people from voting, although it’s very hard to determine how many.

“The thing I’m concerned about is that it will lead to confusion on Election Day,” said Nathaniel Persily, who teaches election law at Columbia University in New York. “There will be spotty enforcement ... and there could be lines and slow voting as a result.”

Michael J. Pitts, who teaches election law at Indiana University, said Pennsylvania’s decision is distinctive because of the court’s discomfort with changing voter identification requirements so close to an election.

The law was a signature accomplishment of Corbett and Pennsylvania’s Republican-controlled Legislature, which passed it over the objection of every Democratic lawmaker. Republicans, long suspicious of ballot-box stuffing in the Democratic bastion of Philadelphia, justified it as a bulwark against any potential election fraud.

Democrats, accusing Republicans of using old-fashioned Jim Crow tactics to steal the White House from Obama, turned their opposition to the law into a valuable tool to motivate volunteers and campaign contributions.

Other courts have issued conflicting rulings on strict photo ID provisions. A federal court panel struck down Texas’ law, while a state court blocked Wisconsin’s voter ID law from taking effect for now. A federal court is reviewing South Carolina’s law.