Boston Mayor Marty Walsh drew a labor-union line from his recovery from alcoholism, through his policies as mayor, to undermining Republican presidential nominee Donald Trump’s business experience building skyscrapers Monday during a speech at the Democratic National Convention in Philadelphia.

After chants of “Marty, Marty,” from the Massachusetts delegation died down, Walsh introduced himself as an alcoholic. Walsh described hitting rock bottom in 1995, and credited the building trades with getting him the help he needed.

“Everybody was losing faith in me,” Walsh said. “Everybody except my family and the labor movement.”

Twenty years later, as mayor of Boston, Walsh said he similarly wants to give people “a fair shot and a second chance,” offering his plan for tuition-free community college for Boston Public Schools students as evidence.

Walsh’s lifelong labor ties are perhaps more fraught at home, after two members of his administration were indicted for allegedly forcing a music festival to hire union labor—but that didn’t keep him from making labor the through line of his speech.

Walsh's support of Clinton helped her win the Massachusetts primary in the face of a more vigorous than expected challenge from Sen. Bernie Sanders in March.

Last week, Donald Trump Jr. tried to establish his wealthy father’s blue-collar bonafides, speaking about he and his brothers and sisters being the only children of billionaires as comfortable on construction equipment as in cars.

Walsh sought to undercut that line of reasoning, highlighting charges that Trump didn’t pay workers like carpenters and electricians.

“We may not have our names in gold outside any of the buildings we’ve worked on,” Walsh said. “But our sweat, our work, our pride is on the inside of every single one of them. Hillary Clinton knows that.”

Walsh also said Hillary Clinton would help Americans get the “skills, jobs and childcare,” they need.

“There’s no doubt in my mind Hillary Clinton is the champion American workers need,” he said.