To the UK anon who asked about double voting.
To be clear, it would be illegal for a person to mail-in a vote and a vote in person.
But the problem is that mail in votes are usually not counted until later.
Now, some counties may have their voter roll up to date and say, sorry, you asked for a mail-in ballot and you are not eligible.
Then, they would vote a conditional paper vote.
I have never asked for absentee ballot.
and have def not asked for one and then tried to vote, but maybe harder to do than we think.
But if you have a crooked place like chicago, california, they would probably let you vote and then count your ballot also.
However, you could also be registered in two places. vote one by mail in and one in person..in different jurisdictions and may never get caught.
We don't have a national voter's roll