John Fund, writing in National Review:
North Carolina’s State Board of Elections is referring evidence to prosecutors that five people appear to have voted in both North Carolina and in Florida. The information the board is passing on wasn’t gathered by government officials, but by a private watchdog group called the Voter Integrity Project.
This specific problem isn't one that would have been stopped by photo ID. But it is one that would have been stopped by taking vote fraud seriously.
As it is right now, under our current voter-registration system there is almost no chance of individuals who register and vote illegally in more than one state being caught because states do not run comparisons between their voter registration lists.
If they did try to purge their voter rolls of ineligible voters, they'd be accused of racism and of oppressing poor people.