“I have a personal history of intervening in labor negotiations and not negotiating for people: let them negotiate, but sitting at the table,” Walsh, a former Boston mayor, said in an interview. “I want to get to the table before that, before it goes bad, if I need to.”

Labor leaders are happy with that philosophy. Walsh “has taken a very hands-on, proactive approach to these strikes,” AFL-CIO President Liz Shuler told POLITICO. “He’s been out on picket lines. He works behind the scenes.”

“A lot of people think if it’s not out in the news, it’s not happening,” Shuler said. “But there is so much going on on a day-to-day basis that he’s involved in: often behind-the-scenes negotiating and mediating with companies and unions to try to reach agreement, and playing a very active role unlike any other secretary we’ve seen.”

Some Republicans are suspicious of Walsh’s motives, especially given the department’s more aggressive stance on other workplace issues.

“It is abundantly clear that his willingness to serve as a mouthpiece for Big Labor supersedes his obligation of upholding impartiality,” Rep. Virginia Foxx (R-N.C.), the ranking member of the House Education and Labor Committee, said in a statement.

But some business groups are willing to see if Walsh’s strategy can work — particularly if it can head off major economic disruptions.

“He thinks he can be a fair dealer, and I’ve no reason to doubt him on that point,” said Ed Egee, the National Retail Federation’s vice president of government relations and workforce development. But “if you’re going to do that, job No. 1 should be the West Coast ports. That’s hugely important to our members [and] it’s hugely important to the supply chain.”

With pandemic restrictions morphing slowly into the new normal, Walsh will be free to play an even more active role. The DOL head had to oversee the rollout of complex standards regulating Covid-19 in the workplace; take swift action to try to mitigate supply chain constraints; and travel extensively to lobby on behalf of Covid-relief legislation — all while dodging speculation he would run for governor of Massachusetts.

The ripple effects of the percolating conflicts involving the International Longshore and Warehouse Union and the Major League Baseball Players Association will be highly visible — and in the case of the ports, economically painful — to voters if things drag out at a politically pivotal time in Biden’s term.

This summer, the companies that operate ports along the West Coast must renegotiate their multiyear contract with the union that represents thousands of dockworkers. When it last expired in 2014, there were strikes and consequent supply chain disruptions.

“The economy was hemorrhaging roughly a billion dollars a day, and it was something that obviously had great potential to have an even more disruptive effect,” said Tom Perez, President Barack Obama’s labor secretary at the time, who is now running for governor of Maryland.

Perez helped broker a deal after Obama sent him to California to intervene, with the approval of both sides.

The risk of a repeat this year comes with even more on the line, with inflation at record highs — partly due to pandemic-related port backups — and the midterm elections fast approaching.

“If I need to [intervene], I would,” Walsh said. “I absolutely would love to do that.”

ILWU did not respond to multiple requests for comment.

Labor and business interests are also watching closely to see if Walsh will weigh in on escalating tensions in professional baseball. On Tuesday, MLB announced the cancellation of some early-season games as team owners and players remain at odds, with more cancellations on the way absent a deal in the near future.

So far, the most visible example of Walsh’s approach was back in his home state.

In December, the secretary helped seal an agreement in Massachusetts between nurses at Saint Vincent Hospital in Worcester and its corporate owners at a meeting Walsh pushed to hold, bringing an end to a strike that spanned roughly 300 days.

Julie Pinkham, the executive director of the Massachusetts Nurses Association, said Walsh’s “gravitas” was instrumental in holding together a tentative deal as the parties hammered out final details in the lead-up to their meeting with the secretary.

“He was the right person at the right time to put the settlement in motion,” said Pinkham, who has known Walsh since his time as a state legislator.

A spokesperson for the hospital declined to comment.

Pinkham said Walsh had been keeping tabs on the situation in the months prior to jumping in directly.

“Marty is not gonna write a press release about it,” Pinkham said. “That’s not his thing.”

But not all of Walsh’s work is below-the-radar. The Labor secretary made headlines last year when he became one of the first sitting Cabinet members to accept an invitation to visit a picket line — in this instance, a weekslong work stoppage at some of Kellogg’s biggest facilities.

Walsh said he went “not necessarily to walk a picket line, [but] to build a relationship. If the company called me, reached out to me, I would absolutely sit with them and talk to them.”

Walsh’s pragmatic approach to labor negotiations as mayor of Boston won him some support from business groups before his confirmation, though some conservatives remain suspicious of his ability to act as an honest broker.

Foxx and other Republicans have sent a pair of letters to the Labor Department asking for information about Walsh’s dealings on labor negotiations, which they say have been met with silence.

“Is he too afraid to own up to his own political activism, or is he evading accountability to shield his ties to his union benefactors?” Foxx said. “The longer he takes to respond, the more apparent the latter becomes.”

Despite the symbolic importance of the Cabinet position, Labor secretaries have little concrete power to break impasses outside of invoking the Taft-Hartley Act, which allows an administration to intervene in strikes that create a national emergency — a non-starter for Democrats, in particular.

“That’s something Republican presidents do,” Perez said. “That’s not something we do. We believe in collective bargaining.”

Former President George W. Bush did exercise the law in 2002 to reopen the West Coast ports amid a lockout by employers, the first time that part of the 1947 statute had been successfully invoked since the Nixon administration.

Labor secretaries also do not have much ability to inject themselves into labor negotiations without an invitation from the parties involved — as in the case of baseball, where both sides have yet to indicate an interest in taking Walsh up on his offer to wade in.

Administrations more commonly try to use the weight of the secretary’s office to jolt negotiations, though it is done sparingly so as to not to sap its political effectiveness or expose the president to backlash.

“The risk is failure. The risk is egg on your face,” said Nelson Lichtenstein, a labor historian at the University of California, Santa Barbara.

President Bill Clinton jumped at the chance to try to save baseball during the last major standoff — a gambit that backfired when a prospective deal to go to binding arbitration, being negotiated at the White House, fell apart. Clinton’s labor chief, Robert Reich, recently implored Walsh to not repeat the folly.

Obama stayed hands-off from the nitty-gritty of pro sports standoffs during his tenure, though his administration did work to resolve both the situation at the West Coast ports in 2015 and between Verizon and its unionized workers a year later.

“We often live in a world of false choices,” said Perez. “You’re either on the side of labor, or you’re on the side of management, but you can’t do both. That’s a false choice. We can do both.”