HARRISBURG — A summer trial on a constitutional challenge to Pennsylvania’s voter identification law appears likely, but it is less clear whether the central provision requiring voters to show photo ID at the polls will be enforced in the May primary election.

Commonwealth Court Judge Robert Simpson discussed scheduling issues with lawyers at an hour-long meeting Thursday and said he would issue an order within two weeks.

In October, Simpson blocked the photo ID requirement for the Nov. 6 election. He said he was not convinced that, based on guidelines from the Pennsylvania Supreme Court, the state had made it possible for voters to easily obtain acceptable IDs. Under the ruling, poll workers last month were allowed to ask voters to show a photo ID, but not require it as a condition for voting.

The law is fully in effect now as the court prepares to consider the constitutional implications of a lawsuit filed in May on behalf of plaintiffs that include 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.

Senior Deputy Attorney General Patrick Cawley urged the judge to fast-track the case so that the state’s high court could resolve any appeals before the May 21 primary.

Simpson said he was leaning toward a summer trial, citing potential scheduling conflicts if the case were squeezed into early 2013, and hoping to issue a ruling by August so appeals could be decided before the November general election.

Lawyers for the plaintiffs said a compressed scheduled would not leave enough time to thoroughly develop and litigate the case.

Michael Rubin, a Washington, D.C.-based attorney who spoke for the plaintiffs’ legal team Thursday, said they would seek to block enforcement of the photo ID requirement until the state Supreme Court fully resolves the “thorny constitutional issues.”

Witold Walczak of the American Civil Liberties Union said at least 100,000 voters were unable to get IDs prior to the last election, but that only about 16,000 IDs have been issued by the Pennsylvania Department of Transportation or the State Department.

“If you have Election Day tomorrow, you’re going to have about 85,000 people who are disenfranchised,” said Walczak.