Voter fraud has not been a significant problem in the past, so I'm not sure why it is being so much discussed this year. Trump is afraid he's going to lose, and is looking for an excuse already. More and more states are requiring ID to vote, and in order to make a difference in the outcome, there would have to be a huge number of people participating in the activities of voter fraud. I don't believe it is a problem at all.
I'm sure it's an issue in some districts, but several recent analyses show no evidence of voter fraud. An article in the Examiner concluded that "a project part of a Carnegie-Knight News21 initiative headquartered at Arizona State University's Walter Cronkite School of Journalism — finds that there is little evidence to prove that voter fraud is as widespread as some politicians and activists claim." Ultimately most cases weren't even successfully prosecuted.
Voter fraud is not a significant problem in the United States. The number of incidences is negligible. This is tracked by the Federal Election Commission, a non-partisan governmental agency. In an earlier time, voter fraud was much more widespread, but that is no longer the case as there is now increased oversight.
Individual voter fraud is a tiny tiny blip on the radar of our broken voting system. Of much more concern should be the proprietary closed systems of the electronic voting machines. It is much easier to hack a database than to spend all day running around voting at different locations.