Let's make it easy. Make federal presidential election rules that everyone who votes must show picture ID. No exceptions!
That ought to cut fraud considerably.
Then punch a hole in the picture ID when that ID is used to vote.
One punch, one picture, one vote.
By the way, record WHO gets mailed EACH absentee ballot, and compare that to the census and the IRS..
That and making every voter dip his or her right thumb in permanent flourescent orange dye before exiting the polling place.