The recent much-noted New Yorker piece eviscerating Hans Von Spakovsky touches on this topic:
Von Spakovsky offered me the names of two experts who, he said, would confirm that voter-impersonation fraud posed a significant peril: Robert Pastor, the director of the Center for Democracy and Election Management, at American University, and Larry Sabato, a political-science professor at the University of Virginia. Pastor, von Spakovsky noted, had spoken to the U.S. Commission on Civil Rights about being a victim of election fraud: voting in Georgia, he discovered that someone else had already voted under his name.If this was a serious problem, there should be many living voters arriving at the polls to discover someone else had stolen their votes. In fact, even if absentee voting fraud was common, the same sort of thing should happen. Now, you might claim that the reason this doesn't happen is because there are all sorts of dead and imaginary voters registered, so that there's no risk of a real honest human asking for their legitimate ballot and being denied because "Mickey Mouse" had already voted or whatever, but that's a voter registration problem, not a polling place problem.
When I reached Pastor, he clarified what had happened to him. “I think they just mistakenly checked my name when my son voted—it was just a mistake.” He added, “I don’t think that voter-impersonation fraud is a serious problem.”
Anyway, I know no amount of rational examination of this issue is going to make it go away (Chris Hayes compared voter fraud believers to climate deniers this morning on his show, and I think the comparison is apt - both groups deny reams of evidence to continue believing in improbably large secret conspiracies to rig systems toward some desired outcome) but at least it's one more bullet to fire.