Democratic presidential candidate Bernie Sanders is going further than even some advocates of a criminal justice overhaul have in calling for prisoners to have the right to vote.
  
Restoring voting rights to convicted felons released from prison has become a prime Democratic cause. Activists see restrictions on felony voting as a legacy of the post-Civil War era when states devised ways to keep blacks from voting.
  
But even those activists have hesitated to push the idea of extending the right to vote to those behind bars.
  
There's no hesitation, however, for Sanders.
  
During a CNN town hall on Monday, the Vermont senator called for just that. He even acknowledged it would inevitably become a Republican attack ad.
  
Some Sanders' rivals balk at going that far or oppose letting prisoners vote.