gnu, Mellencamp has been involved in some ways in politics, both local and world-wide, for years. Just not as an elected official.

Alex, thanks for the correction on Sonny B. But it doesn't change the point. His entry into politics was as Mayor of a decent-size city, just as Clint Eastwood's was.

To make the point from a slightly different angle:
Why does no one bat an eye when a non-entertainment, non-sports business person, educator, doctor, or someone in sales runs for office, even using their name recognition if they're well-known in the community -- but then cry "foul" if it's a sports figure or entertainer who runs?

I can see why some people might prefer that our politicians have backgrounds in law or maybe (non-sports, non-entertainment) journalism. But I don't see why being in sports or entertainment qualifies you less for holding public office than most other occupations do.