HARRISBURG — A tough new voter identification law championed by Republicans can take effect in Pennsylvania for Nov. 6’s presidential election, a judge ruled today.

Commonwealth Court Judge Robert Simpson said he would not grant an injunction that would have halted the law, which requires each voter to show a valid photo ID. Opponents are expected to file an appeal within a day or two to the state Supreme Court as the Nov. 6 election looms.

“We’re not done, it’s not over,” said Witold J. Walczak, an American Civil Liberties Union lawyer who helped argue the case for the plaintiffs. “It’s why they make appeals courts.”

The Republican-penned law has ignited a furious debate over voting rights as Pennsylvania is poised to play a key role in deciding the presidential contest. Plaintiffs had asked Simpson to block the law from taking effect in this year’s election as part of a wider challenge to its constitutionality.

Republicans defend the law as necessary to protect the integrity of the election. But Democrats say the law will make it harder for people who lack ID for valid reasons to vote.