A Pennsylvania judge on Wednesday declined to block a new state law requiring specific kinds of photo identification to vote. Liberal groups, arguing that minorities and the poor would be disproportionately deprived of the ballot, said they would appeal to the State Supreme Court to stop the law before the November elections.

The groups said the law, like those recently passed in 10 other states, was a Republican attempt to suppress participation of the less privileged, who tend to vote for Democrats. The laws’ backers said they were seeking to preserve the integrity of the electoral process.

Both parties acknowledge that voter turnout could play a crucial role in what many predict will be a tight race between President Obama and Mitt Romney, the presumptive Republican nominee, especially in battleground states like Pennsylvania. Other court cases under way include federal inquiries into voter ID laws in Texas and South Carolina and a state challenge in Wisconsin. In Ohio, a dispute over rules for early voting ended on Wednesday when the secretary of state set uniform hours statewide.

In his ruling on Wednesday, Judge Robert Simpson of Pennsylvania, a Republican, said that there might have been a partisan motive behind the law and that it might indeed cause difficulties for tens of thousands of voters on Nov. 6. But neither matter is enough to stop it, he concluded, because judgments from both the state and federal Supreme Courts give legislatures leeway to regulate voting unless done in a clearly discriminatory or burdensome way. The Pennsylvania law, he said, passed muster.