I actually had some theoretical opportunity to engage in voter fraud and vote twice about 20 years ago.
The way it works in Texas is that each voter is assigned to a specific precinct, and they’re expected to vote at the designated polling place for that precinct, usually a school, church, library, or government building of some sort. The election workers have a record of who’s registered at that precinct, and they check each voter against that list- used to be a printed ledger that they looked you up in and you signed next to your name. Now it’s electronic, but you still sign a signature pad.
(this is one mechanism of voter suppression; in white areas, the polling places are numerous and widespread making voting easy, while in non-white/poorer areas, they’re further apart and less convenient, causing long lines, frustration and difficulty in getting to them).
I had moved from Houston to DFW in August of 1999, and re-registered to vote in Collin County as I was supposed to do. Come November, I voted in Collin County and everything was fine.
However, whatever record-keeping and information transfer process apparently hadn’t been completed by the time of the next election, because I got a call from my dad a day or two later where he asked if I’d registered to vote in Collin County yet. I told him I had, and he told me that I was still on the voter rolls at the old precinct there in Houston- he saw my name below his when he was signing his name.
So in theory I could have voted in both places because I was still on the rolls in both places. But the chance was totally due to bureaucratic incompetence, not some nefarious doings on my part.