Walsh’s surprise supporters

Sure, Marty Walsh has labor with him as he steps up his quest to become Boston’s next mayor.

But he also has Joyce Linehan, a prominent Dorchester activist and darling of Bay State progressives. In the nuanced world of Boston politics, that sets him apart from other union-backed politicians — and gives him a crack at the city’s liberal constituency in a race that will turn on turnout.

Linehan presides over what Commonwealth Magazine writer and Globe contributing columnist Paul McMorrow recently called “the most famous living room in Massachusetts politics.”

A few summers ago, that living room helped launch Elizabeth Warren’s run for US senator. At Warren’s request, Linehan packed in a crowd of local citizens who were searching for a candidate. That night, they fell in love with Warren and went on to become part of her grass-roots campaign organization. Ever since, liberal Democrats clamor for an opportunity to make their pitch to Linehan’s network of friends and activists, in the sanctity of her salon.

In the Boston mayor’s race, Linehan came out early for Walsh. She’s a passionate advocate for the longtime labor leader and state representative from Dorchester, who is also a personal friend. On the weekend before the preliminary election, she posted a pro-Walsh testimonial on bluemassgroup.com, the popular liberal website. Under the headline “Why Marty?” she addressed the issue of why “my progressive bona fides are seldom questioned, while people assume that he is just another in a long line of white Irish Catholic guys from Dorchester.”

She and Walsh, blogged Linehan, “share core values: equality, access, transparency, and social justice. I believe he’s the most progressive candidate in the race, but more importantly, he is positioned to be the most effective, able to bring disparate voices to the table and convince them to work together.”

Walsh begins his run-off against City Councilor John Connolly with the benefit and burden of serious union support. In the run-up to the preliminary election, he was frequently asked about his ability to stand up to his union brethren, given the money and organization they were contributing to his campaign. Walsh’s answer: Labor would trust him at the negotiating table when he told them he could go no further with pay and benefits.

That answer won’t suffice in his showdown with Connolly. If Connolly is cast as the brave reformer who is ready to take on the public unions and Walsh is defined as the guy who will tell those unions he has given them all he can, then Walsh loses. However, if Walsh is cast as the mayor who can bring everyone to the table and Connolly is seen as too polarizing, then Walsh has at least a shot at changing the negative narrative that began during the preliminary election campaign. And at that point, only one public union representing Boston firefighters had endorsed him; he was mainly endorsed by building trade unions, with whom the city does not negotiate.

The Walsh campaign understands the stakes. The goal is to quickly get out the message that Walsh is more than the labor candidate. He is also the candidate of the Linehan-left. To that end, Walsh will stress his pro-human service voting record in the state legislature and his focus on substance abuse, due in part to his own struggles with alcohol.

Those are among the issues that appeal to Linehan, who, in a recent interview, described Walsh as a “scrappy fighter” for many causes dear to progressive hearts. Walsh, she said, led the fight on Beacon Hill to prevent a ballot question repealing gay marriage after the Supreme Judicial Court affirmed marriage equality in Massachusetts. She also points to his backing for a program called “Building Pathways,” which champions women and people of color for union apprenticeships.

She acknowledges that the public perception that unions are “out for number one” can hurt Walsh. “It’s on the unions to redefine the conversation,” she said.

There’s not much time to do it.

On Tuesday, Connolly’s side joked that not a single hammer or saw was being used in eastern Massachusetts because their union owners were getting Walsh voters to the polls. Walsh will need more powerful testimony from Linehan and others to overcome punchlines like that.