Tom Barrett wants a second shot at Scott Walker. The 58-year-old mayor of Milwaukee lost to Walker by nearly 125,000 votes in Wisconsin's 2010 gubernatorial election, a bitterly fought race in a tea party-fueled GOP landslide year. Now, 18 months later, Walker's anti-union and staunchly conservative agenda has divided the state and created the momentum for a June 5 recall election. The populist outrage will favor the Democrats, and the polls show Barrett is best-positioned to oust Walker. But first he must win his own party's nomination in the May 8 primary—and that's no lock.