By Dave Warner

PHILADELPHIA (Reuters) - The national debate over voter identification laws comes to Pennsylvania's Supreme Court on Thursday with challengers set to argue that the state law will shut out thousands of minority voters.

The Pennsylvania law, which requires all voters to show either a state driver's license, government employee ID or a state non-driver ID card, has been under fire from the American Civil Liberties Union and other legal organizations, following similar battles in Texas and South Carolina.

Supporters say the law, passed by a Pennsylvania's Republican legislature, will prevent voter fraud but critics say its true aim is to limit minority voters, who tend to vote Democratic.

The ACLU and the Advancement Project, a multi-racial civil rights organization, are among several groups that filed a lawsuit seeking an injunction from the state's highest court less than two months before Election Day.

"This law deprives many eligible voters in the commonwealth - disproportionately the poor, minorities, senior citizens, young voters and people with disabilities - of their fundamental right to vote," said Judith Browne Dianis, co-director of the Advancement Project.

Because there are "zero instances of in-person voter fraud in Pennsylvania," the law will serve instead to exclude several hundred thousand Pennsylvanians, said Witold Walczak, legal director for the state ACLU.

"Why do we need to do this? There is no reason," Walczak said.

Arguing against the injunction is the state attorney general's office, which maintains that opponents failed to show the law causes any immediate harm.

The legal battle takes place against the backdrop of a widely reported statement by Republican House Majority Leader Mike Turzai, who was quoted as saying, "Voter ID, which is going to allow Governor Romney to win the state of Pennsylvania - done."

Turzai's press secretary, Steve Miskin, told Reuters this week that the quote is accurate but widely mischaracterized.

He said his boss, who represents the Pittsburgh area and was speaking at a party meeting in June, meant that "for the time in many years we are going to have a presidential race on a relatively level playing field."

Pennsylvania's Supreme Court currently has six justices - three Democrats and three Republicans, raising the possibility of a tie. A seventh judge was suspended while she faces criminal charges for improperly using staff for political campaigns.

A tie would keep in place an earlier ruling by a lower appellate court that refused to issue an injunction, according to Supreme Court spokesman Jim Koval.

(Editing by Barbara Goldberg and Bill Trott)