Gov. Chris Gregoire has endorsed Seattle mayoral candidate Joe Mallahan.

Seattle mayoral candidate Joe Mallahan, who was barely known in Seattle political circles just a few months ago, added a big name to his endorsement list Thursday: Gov. Chris Gregoire.

A spokeswoman for Gregoire said Mallahan sought the governor’s endorsement and she agreed, in part because Mallahan agrees with her that a tunnel should replace the Alaskan Way Viaduct.

Gregoire and other state and local leaders worked for years on an agreement about how to replace the viaduct.

Mallahan’s opponent, Mike McGinn, says he will try to undo the deal if he is elected. McGinn, a former Sierra Club chairman, believes the tunnel is too expensive and encourages reliance on cars. He supports improving surface streets and transit after the viaduct is torn down.

Unlimited Digital Access. $1 for 4 weeks.

In a statement, McGinn said: “Joe Mallahan supports the tunnel and says ‘we can live with’ city residents paying cost overruns on a state highway. I’m sure Olympia, the governor and state legislators would prefer a mayor that ‘can live with’ billions in potential cost overruns from Seattle’s big dig. I won’t be that mayor.”

Mallahan, a T-Mobile vice president who has contributed $230,000 to his own campaign, has picked up many major endorsements since the August primary. He has the support of most major unions, the King County Labor Council and elected and business leaders. Most of his endorsers also think the city should move forward with the tunnel.

In a press release Thursday, Gregoire didn’t mention the tunnel specifically.

She said: “Seattle’s next mayor needs to be someone who understands that rebuilding Seattle’s economy and creating family-wage jobs must be the top priority of their administration. To do that, the mayor must be someone with proven experience and a willingness to work closely with Seattle’s diverse citizens, businesses, unions and state and local elected officials. The candidate in this race who has those qualifications is Joe Mallahan.”

Gregoire spokeswoman Kelly Evans said the governor has also endorsed Dow Constantine for King County executive. Evans said the governor often will endorse in local elections if the outcome is of particular importance, if someone seeks her endorsement or if the person running is a friend.

The governor had not met Mallahan until she and Mallahan recently sat down in Seattle, Evans said.

Mallahan said in the release he is “deeply honored” to have the governor’s endorsement.

Ballots in the all-mail election must be postmarked by Nov. 3.

Emily Heffter: 206-464-8246 or