Not everyone wants to be the background music for a political campaign, and John Mellencamp knows that all too well. He recently (re)shared his sentiments with Wisconsin Gov. Scott Walker, exclaiming that he is a supporter of union rights and wants Walker to remember that during his campaign. This may not come as a shock since Mellencamp was not shy to explain why he is not a fan of his song "Small Town" being used for the Republican's campaign in 2012, either (kinda sounds familiar, right?). "He's a very liberal person," Mellencamp's publicist Bob Merlis said of the singer. "He appeared at the Democratic National Convention in 2004. His wife at the time was a delegate at large....