They still live and are protected by their country.
It heavily depends the crime. Murder, no. Heavy drugs such as meth, no. Rape, no. Light drugs, such as weed. Yes. etc
Yes. Prisoners have a useful look on the world. Going through the things they have to end up where they are makes them uniquely aware of the problems in this country. Plus being away from media and harassment may make them pleasantly impartial.
They have committed a crime against the State, why then should they have any say in how it is run? You commit a crime you lose your liberty, and that includes the right to vote.
Not while they are in prison. When they finish their sentence, they may vote.
It would be obvious for someone that wants to run for a political office to not only say what they think people that are making a difference in society want to hear but there going to say thinks that prisoners are going to hear like shorter sentences. Plus those people lost there chance at voting when the went against the law