Whoever gave Bernie the idea of a platform stand, this prison vote idea, where all Americans in prisons (county, state, federal) would have the right to vote....has hit some rough acceptance, even with Democrats.
Logistically, it has problems that you can't really imagine.
An example: Say you live in Texas (own a house, and registered to vote there), and you did some stupid stuff in Oregon on a trip, got arrested....charged-up....convicted....and will be in the Oregon prison for twelve years. Are you still registered via Texas, or is your new residence Oregon? Who will decide your residence, and thus your vote?
Another example: Lets say you did some stupid stuff, and got yourself into a Venezuelan prison (overseas). Just how much effort will the US government have to attend to.....to get the Texas ballot to you, and guarantee your vote?
Another example: You are on death-row, and the election is three months past your execution date. You go to the judge and demand the right to either vote early, or extend your execution date till the day after the election.
I don't see the problem in handing back the right to vote to a guy after he has served his full sentence and exited the prison or jail. But if you insist that this right is something to fight over, why couldn't you allow the same guy to have the right to bear arms (own a gun)?
Bernie opened up a can of worms, and I suspect that fifty percent of Democrats won't buy into the vote idea, and it might well cancel out the half of 2016 states that he won in the primary.