a fingerprint to vote would do wonders here.
Unfortunately, it wouldn't do much about some of the dead who still seem to vote (crooked poll watchers) and ballot box stuffers (corrupted custody chain).
I'd say the stained finger is about one of three additional measures we should take here. Another one being a complete re-regstration, (2-photo IDs (match photos to person, scans of both IDs and facial measurement scan for the records), with addresses, and US mail, stamped and postmarked (not metered), delivered to the person at ID address) and no one who hasn't passed the process 30-days in advance gets to vote.
The third would be a very aggressive, cross-correllated follow-up on the ID, with stiff sentences for fraud--not necessarily tied to the actual act of voting.