"Article 1. All United States citizens of age 18 or older, not physically incarcerated, and not found mentally incompetent by a court of law, have the right to vote in all elections in the state and locality where they reside.
Article 2. The efforts of governments to ensure that persons not eligible to vote under Article 1 are prevented from voting must not impose obstacles that have the effect of making the exercise of the franchise more difficult for those entitled to vote under Article 1."
Yes, let's go all Founding Fathers and italicize 'effect' for emphasis. Screw intent: if a law intended (or 'intended') to prevent voter fraud makes it more difficult for persons eligible to vote to vote, then it should get tossed.
Also, this amendment, while not requiring states to allow persons physically in prison or jail to vote, would require that persons out of jail couldn't be prevented from voting due to having served time in prison, or being on parole or probation. If you're not actually in the pokey on Election Day, you should be able to vote.