The state of Pennsylvania has adopted legislation requiring voters to present a photo identification to cast their ballots, joining 15 other states that have passed similar provisions.

The bill was officially signed into law late Wednesday by Republican Gov. Tom Corbett, after passing on largely party-line votes in the state’s House of Representatives and Senate, as most Republicans backed it and Democrats opposed it.

The law, which civil rights groups say could disproportionately affect the voting of blacks and other minorities, mandates that voters present a government-issued ID, a student ID or photo identification from a nursing home, assisted living home or personal care home in order to vote.

Republicans say these provisions can prevent voter fraud, although there is little evidence that fraud is a problem, in Pennsylvania or nationally. Democrats, including the Obama administration, cast them as unnecessary barriers to voting, particularly since minorities disproportionately don’t have driver’s licenses, although voter turnout among blacks actually increased even after Georgia enacted one of these laws.

“I believe we need to ensure that our elections are fair,” Corbett said, in a signing ceremony on Wednesday.

In states from Rhode Island to Texas, voter ID laws have passed over the last year. Some, like in Texas, would make it harder to use a student ID to vote, but most allow a variety of forms of identification. But civil rights groups have successfully challenged a similar provision in Wisconsin, and the Department of Justice, using its power under the Voting Rights Act, has blocked the adoption of these laws in South Carolina and Texas.

The Pennsylvania provision is almost certain to be challenged in court by the American Civil Liberties Union. And it is likely be closely watched by both proponents and opponents of voter ID laws.

While many of the photo identification provisions have been adopted in heavily conservative states like South Carolina and Texas, Pennsylvania is a key state President Obama will need to capture to win reelection.