Lawyers hoping to persuade Commonwealth Court Judge Robert Simpson to stop the law from taking effect brought voters to court to testify about hurdles they say they've encountered in trying to get a valid ID.
Simpson has hinted that an injunction is possible before the Nov. 6 presidential election, but said he would not issue his decision in court Thursday, the third and final day of testimony in the latest chapter of a legal challenge to the 6-month-old law.
Under a state Supreme Court order, the judge has until Tuesday to rule.
The new law is among the toughest in the nation and the Pennsylvania case has become a political lightning rod in the contest between Democratic President Barack Obama and Republican presidential nominee Mitt Romney for the state's prized 20 electoral votes.
Republicans, long suspicious of ballot-box stuffing in the Democratic bastion of Philadelphia, maintain that the law will deter election fraud. But Democrats point to a blank trail of evidence of such fraud, and charge that Republicans are trying to steal the White House by making it harder for the elderly, disabled, minorities, the poor and college students to vote.
The new law requires each voter to show a particular form of photo ID, such as a driver's license, passport, active duty military identification, nursing home ID or college student ID. The prior law required identification only for people voting in a polling place for the first time and it allowed non-photo documents such as utility bills or bank statements.
Simpson initially denied the request for a preliminary injunction in August, saying the plaintiffs did not show that "disenfranchisement was immediate or inevitable." But after an appeal, the Supreme Court directed him to use a much tougher standard for tolerating voter disenfranchisement.
The high court ordered him to halt the law by Tuesday if he finds the state has not met the law's promise of providing free and easy access to a photo ID or if he believes it will prevent any registered voters from casting a ballot.
Lawyers for the plaintiffs say registered voters continue to be turned away from state driver licensing centers without a photo ID. They cite burdensome and complicated requirements that ill-informed clerks at the license centers have handled poorly.
State officials say they believe the number of people who need an ID to vote is small - the state had issued less than 11,000 free IDs as of Monday - and they contend that an 11th-hour overhaul in the requirements for someone to get a voting-only photo ID should comply with the Supreme Court's directions.