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.
The voter ID law was a signature accomplishment of Pennsylvania's Republican-controlled Legislature and its Republican governor, Tom Corbett. Republicans, long suspicious of ballot-box stuffing in the Democratic bastion of Philadelphia, justified it as a bulwark against any potential election fraud.
Democrats objected furiously, accusing Republicans of using old-fashioned Jim Crow tactics to steal the White House from Obama by making it harder for young adults, the poor, minorities and the disabled to vote.
Protests, warnings of Election Day chaos and voter education drives ensued, as the law's opponents began collecting stories of people who had no valid photo ID and had encountered stiff barriers in their efforts to get one from state driver's license centers.