His ruling came after listening to two days of testimony about the state's eleventh-hour efforts to make it easier to get a valid photo ID. He also heard about long lines and ill-informed clerks at driver's license centers and identification requirements that made it hard for some registered voters to get a state-issued photo ID.
The 6-month-old law — now among the nation's toughest — has sparked a divisive debate over voting rights and become a high-profile political issue in the contest between President Barack Obama, a Democrat, and Republican nominee Mitt Romney, for Pennsylvania's prized 20 electoral votes.
Pennsylvania, traditionally considered one of the most valuable a presidential swing states, is showing a persistent lead for Obama in independent polls. As a result, the state has been virtually empty of presidential TV ads and off the candidates' beaten paths to more contested states in recent weeks.
Pollsters had said Pennsylvania's identification requirement could mean that fewer people ended up voting and, in the past, lower turnouts have benefited Republicans in Pennsylvania.
But Democrats have used their opposition to the law as a rallying cry, turning it into a valuable tool to motivate volunteers and campaign contributions while other opponents of the law, including labor unions, good government groups, the NAACP, AARP and the League of Women Voters, hold voter education drives and protest rallies.