A rare contested race for the International Association of Fire Fighters (IAFF) presidency has given its members a choice between a union traditionalist from Boston and a progressive activist who backed massive labor protests against Wisconsin governor Scott Walker a decade ago, then joined electoral efforts to oust the anti-union Republican.

In mail balloting already underway, local union delegates are casting votes on behalf of 320,000 IAFF members throughout the United States and Canada. They are choosing a replacement for seventy-five-year-old Harold Schaitberger, a full-time union official for more than four decades and a longtime mover and shaker in national Democratic Party circles, who announced his retirement last fall. Vying to succeed him are IAFF secretary-treasurer Edward Kelly, a forty-seven-year-old Air Force veteran and former leader of the union’s Massachusetts branch, and Mahlon Mitchell, a forty-three-year-old from Madison, Wisconsin, who heads the Professional Fire Fighters of Wisconsin.

Both challengers are energetic, ambitious, and young — by US labor leader standards, anyway. But Kelly more strongly reflects the insular “old school” culture of this public-sector craft union, while Mitchell, a 2016 Democratic National Convention delegate for Bernie Sanders, has favored firefighter alliances with other public workers facing budget cuts or loss of their workplace rights.