Each house of Congress makes its own rules for what its members can and can't do, but the rights of other citizens are decided differently. We need to know: does Sanders have pen pals in prison?
Stay on topic.
I am on topic: Congress makes its own rules for its members and these rules have nothing to do with what other citizens have rights to.
But seriously, why is Sanders chasing the prison vote?
Chasing the prison vote? Give me a ******* break! He is advocating for the rights of American. Prisoners, regardless of what they have done, are still Americans. Oh, and remember , they are disproportionately people of color - which goes a long way in explain the rights aversion to allowing them to vote.