There’s only 3 outcomes here, and all neutral or in your favor:
1: one candidate wins handily, and your vote wouldn’t have mattered anyway;
2: close race, your prov ballot cancels out your imposter’s vote;
3: close race, you and imposter both voted right
The poll workers tell you that someone has already cast a vote in your name, using a water bill envelope as ID. You show your drivers license to cast a provisional ballot, but they’ll only count it, if the vote is close. Have you been disenfranchised?