In its filings in a current lawsuit, the state of Pennsylvania stipulates that it has no evidence of in-person voter fraud, the only type of election tampering that would be addressed by voter ID laws. (Here's a link to a PDF of the actual filing.)
But Pennsylvania has still enacted a voter ID law that threatens to disenfranchise lots of voters, including members of the state's "Voter Hall of Fame" -- about 21,000 Pennsylvanians who has cast votes in every single general election for at least half a century. An analysis suggests that nearly a fourth of those dedicated voters lack a photo ID that meets the state's requirements.
Even if those people have the means to get new photo IDs, it's not clear that the Pennsylvania Department of Transportation, which issues drivers' licenses and official state IDs, could handle the logistics of producing all those new identification cards between now and the election.
Why would the state put itself in the position of taking voting rights away from so many of its citizens? No doubt some legislators genuinely thought the new law was a good idea, not realizing that the problem it addresses is close to nonexistent or that so many citizens don't have photo IDs that meet the law's requirements. Others appear to have had political motives, recognizing that people without a photo ID often tend to have lower incomes and vote for Democrats.
Here, for example, is Pennsylvania House Majority Leader Mike Turzai:
If you can't watch the clip, it shows Turzai cataloging recent Republican accomplishments in the state, including, "Voter ID, which is going to allow Governor Romney to win the state of Pennsylvania -- done!"