SUPERIOR, Wis. ― It was a little early for a drink, but that wasn’t going to stop Mahlon Mitchell. It was a Saturday at 11:30 a.m. in Superior, a port city of 30,000 in Wisconsin’s far northwest corner. Mitchell, the leader of the Professional Firefighters of Wisconsin and a Democratic candidate for governor, had just finished touring the city with fellow firefighters and was about to kick off an economic roundtable with other union members. But first, he was perusing the beer list at Thirsty Pagan Brewing. Why? “I can run faster and jump higher than the other candidates,” he...