I've always felt if you really want to impact election fraud, tax the hell out of votes. Like $1,000/vote. For those who believe in democracy, a handful of votes over a lifetime is all you need, and ideally the right candidate wins anyway.

Could probably create exceptions for local elections, so you can still participate in your community.

Tricky part would be general elections, but restricting such a tax to federal races is probably an 80% solution.