President-elect Joe Biden will nominate Boston Mayor Martin Walsh for Labor secretary, according to two reports Thursday, citing sources familiar with the decision. 

Politico and The Washington Post reported the decision without naming their sources. 

Building trade unions began congratulating Walsh in press releases Thursday.

“We could not be more thrilled with this pick,” said United Association of Union Plumbers and Pipefitters General President Mark McManus in a statement.

Walsh edged out other candidates for the cabinet spot, including California Labor Secretary Julie Su and AFL-CIO chief economist and Howard University professor William Spriggs.

The nation’s largest labor federation, the AFL-CIO, endorsed the Walsh pick Thursday, praising his background as a laborer.

“Boston Mayor Marty Walsh will be an exceptional labor secretary for the same reason he was an outstanding mayor: he carried the tools,” AFL-CIO President Richard Trumka said in a release. “As a longtime union member, Walsh knows that collective bargaining is essential to building back better by combating inequality, beating COVID-19 and expanding opportunities for immigrants, women and people of color.”

American Federation of Teachers President Randi Weingarten also supported the pick. “Workers need a champion in Washington — and Marty Walsh would be a crucial addition to an administration dedicated to fighting for the forgotten and rebuilding an enduring middle class,” she told CQ Roll Call in a written statement.

In contrast to recent Labor secretaries, Walsh is a union man.

He was a lifelong union member before his mayorship, joining the Laborers’ Union Local 223 after college — the same union his father joined shortly after emigrating from Ireland, and the one his uncle ran as president.

Walsh’s cousin — also named Martin — now runs Local 223. He served as the local’s president and was the head of Boston’s building trades council in 2011, representing 35,000 construction workers on virtually every large development in the metro area.

Like Biden, Walsh is a teetotaling Irish Catholic, although Walsh is a recovering alcoholic who’s been sober for more than 20 years.

Republicans immediately signaled their opposition.

“Unfortunately, President-elect Biden’s nomination of Marty Walsh to lead the Department of Labor raises significant concerns about the federal government’s role in shaping the future of our evolving workforce,” said  House Education and Labor Committee ranking member Virginia Foxx of North Carolina in a press release.

But the pick is likely to be popular with many rank-and-file union members, who see Walsh as one of their own. Some may be disappointed that Biden picked someone out of the union trades, which tend to be dominated by white members and have a history of racial discrimination. It may also disappoint Democrats who have urged Biden to make more diverse Cabinet picks.

Walsh’s confirmation could face some hurdles. A jury convicted two of Walsh’s aides of extortion in 2019, but the judge threw out the guilty verdicts in 2020. The aides were accused of withholding a permit to a popular music festival over the organizer’s refusal to hire union workers, which federal prosecutors argued was done as a political favor to Walsh. In dismissing the convictions, the judge said prosecutors failed to prove a quid pro quo existed, among other missing legal elements.

Niels Liesnewski contributed to this report.