BOSTON (CBS) — President-Elect Joe Biden “definitely wants Marty Walsh” to be his secretary of Labor, a person familiar with the decision process tells Politico. But concerns about having enough diversity in a Biden cabinet may lead to a different choice, the publication reports.

Walsh was a longtime labor leader before becoming mayor of Boston in 2014. He is also a strong supporter of Biden, who came to Boston to swear Walsh in for a second term as mayor in 2018.

This isn’t the first time speculation about Walsh joining Biden’s cabinet has arisen. Both Walsh and Vermont Sen. Bernie Sanders were talked about as possible Labor secretaries in November.

“There’s a lot of speculation about a lot of things. There’s a lot of people being tapped. He can’t take everyone from Massachusetts to Washington with him,” Walsh said at the time. “I’m just looking forward to working with this administration as everyone here is.”

Walsh has not officially announced he’s running for re-election as mayor in 2021. City Councilors Michelle Wu and Andrea Campbell have already declared their candidacies.

Politico reports that Biden is “sensitive to the diversity concerns” and that may ultimately derail Walsh’s chance of being picked. While the publication says Biden has nominated “the most diverse cabinet in history,” some groups are still pushing for more diversity in the remaining unfilled positions.