My 7 year old has been very interested. He went with me to vote and wanted to know about every candidate with a sign at the poll. We went on the internet and he looked at several of the videos and made candidate choices with strong conviction (and some good reasoning).
We also got a survey in the mail regarding our opinion on several "hot" political topics. We had no intentions of returning it so I let him have it. That lead to many interesting conversations so he could make decisions to fill out the survey (energy, Iraq, "reproductive rights", etc.). That'll teach me not to give him the mail without screening it better!