Massachusetts had a ballot proposition to let convicted felons vote in prison a few years back. It didn't pass, but I voted for it. The state is at least pretty good about restoring the vote to felons who have served out their terms.

There are a bunch of states, mostly in the South, that disenfranchise felons for life, which seems like the variant most obviously ripe for abuse as well as accidental bad consequences. Of course, the laws were enacted as ways to deny the vote to as many black people as possible without explicitly doing so.