its more the difficulty in getting a photo id if you're poor. Rich people (generally) have cars, houses, jobs, and out of country vacations that require photo id's . So when it comes time to vote, it isn't an issue. A poor person isn't going to have a passport, and theres a lot higher chance they won't even have a drivers license, or a way to get to it. The closest DMV to where i live is a 2 hour drive, and there is no bus to get there. So how does a poor person acquire a photo id?
the controversy of this issue isnt that photo id is bad for the voting system on its own, its the fact that the people who don't have a photo id may not be able to get one, skewing the demographics of who can vote. The other controversial part is there is no proof of current voter fraud influencing elections, so why do people (republicans) decide to care now?