We already have it. Now that Repubblies control more than half of the legislatures, they should (and trust me, will) pass voter ID laws. That might be worth 1% of all ballots during a close election year for a statewide office, because all the fraud happens in heavily Democratic precincts.
Also make the penalties for any kind of vote tampering to be of severe consequences, like 5 years and $10,000 fine that has to be paid before a person can get out of jail. Make it mandatory sentencing without any chance of parole and no cupcake prisons. Federal prison only.