The problem is those id's could be scanned to see if people are using more than one id. Also they fill in ballots for people that have not voted and that would require they have those id's. Which would make cheating harder but you cant eliminate all cheating. I suspect that there is a ton of cheating down ballot by both parties. I know that small town vote fraud is huge. I have no clue if that really effects top of ticket. But with razor margins I think it has too.