At the best of times, most people are not trained hand writing experts. And more and more ballots are being 'signed' using a finger on a touchscreen, making verification virtually impossible. A PKI system solves both issues.
This is the same system used to digitally sign emails across the entire business world, as well as encrypt data.
No fucking computers! Ever! Dump the absentee ballot system or reform it so only military have access and only people that cannot leave a nursing home or people that have a plane ticket to prove they are going out of the country on election day. Also, have them be notarized by a notary public to confirm the signature. DONE.
The notary alone would remove all the lazy people that don't want to wait in line on election day and make it close to bulletproof.