Commonwealth Court Judge Robert Simpson said he wouldn’t grant an injunction that would have halted the law requiring 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 presidential election looms.

The Republican-penned law — which passed over the objections of Democrats — has ignited a furious debate over voting rights as Pennsylvania is poised to play a key role in deciding the presidential contest in November. Opponents 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 the elderly, minorities, the poor and college students to vote, as part of a partisan scheme to help the Republican challenger, Mitt Romney, beat Democratic Obama.

“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.”

Simpson didn’t rule on the full merits of the case, only whether to grant a preliminary injunction stopping it from taking effect.

Votes by four of six Supreme Court justices would be needed to overturn the ruling by Simpson, who is a Republican. But the high court is currently split between three Republicans and three Democrats following the recent suspension of Justice Joan Orie Melvin, a Republican who is fighting criminal corruption charges.

The original rationale in Pennsylvania’s Republican-controlled Legislature for the law — to prevent election fraud — played little role in the case before Simpson since the state’s lawyers acknowledged that they are “not aware of any incidents of in person voter fraud.” Instead, they insisted that lawmakers properly exercised their latitude to make election-related laws when they chose to require voters to show widely available forms of photo identification.

Republican Gov. Tom Corbett signed the law in March after every single Democratic lawmaker voted against it.

At issue is the requirement that all Pennsylvania voters produce a valid photo ID before their ballot can be counted, a substantial change from the law it was designed to replace. That law required identification only for people voting in a polling place for the first time and it allowed non-photo documents such as a utility bill or bank statement.

But some of the people who sued over the law say they will be unable to vote because they lack the necessary documents, including a birth certificate, to get a state photo ID, the most widely available of the IDs that are valid under the law.

The lawyers who provided free legal representation to the plaintiffs also warned that it will be difficult for many others to get a valid ID, and they presented testimony about workers at Department of Transportation license centers who appeared uninformed about the requirement to issue free non-drivers IDs for voting.

In addition, some voters won’t know about the law until they get to the polls and long waits will result while untrained election workers struggle to carry out a complicated and unnecessary law amid the traditionally larger turnout in presidential elections, they argued.

Lawyers from the attorney general’s office, which defended the law, pointed out that the state is planning to begin issuing a special photo ID card for registered voters who are unable to get a PennDOT-issued ID and lack any other photo ID that is acceptable under the law, such as a passport or active-duty military ID.

In addition, they say the state is rolling out a public relations campaign to make people aware of the law.

The Department of State, which oversees elections in Pennsylvania, has not produced any kind of study or survey that estimates the number of people without a valid photo ID that is required by the law.

Meanwhile, Obama’s Department of Justice is looking at whether Pennsylvania’s tough new voter law requiring photo identification complies with federal laws and on Monday asked the state’s top election official and a chief supporter of the law for a long list of information about it.