Embracing the label of “union boss,” state firefighters president and Democratic candidate for governor Mahlon Mitchell rallied organized labor supporters June 11, urging them to unite to elect him in August and then defeat Gov. Scott Walker. Mitchell is one of 10 Democratic candidates for governor, but his position as head of the Professional Fire Fighters of Wisconsin has given him an early advantage in union backing — both in campaign donations and people power. Mitchell previously ran as the Democratic lieutenant governor candidate in the unsuccessful 2012 recall election against Walker.