OLYMPIA — A lobbyist with ties to Republican candidate Dino Rossi is suing supporters of Democratic Gov. Chris Gregoire for defamation because he was mentioned in a political attack ad.

Lobbyist David Ducharme’s lawsuit claims the independent political group Evergreen Progress is harming his reputation, because the ad in question appears to tie him to a campaign financing lawsuit involving the Building Industry Association of Washington.

Ducharme’s lawsuit was filed Monday in King County Superior Court. He’s asking a judge to order the ad pulled off the air. He also wants unspecified damages.

The ad in question opens with images of Rossi, Ducharme and Ducharme’s father, Richard Ducharme. It says “these real estate industry lobbyists” helped Rossi buy an apartment building and a bank.

The ad then goes on to say that “Rossi’s big developer friends” are now embroiled in a campaign financing controversy, including a lawsuit from Republican state Attorney General Rob McKenna — a reference to the BIAW’s recent court case alleging misreported campaign financing.

David Ducharme’s lawsuit acknowledges that he has invested in the two properties with Rossi, but disputes the characterization that he “helped” Rossi buy them. The younger Ducharme also says the ad falsely asserts that he’s a “real estate industry lobbyist,” and falsely ties him to the BIAW fundraising lawsuit.

David Ducharme says he doesn’t work for the BIAW, and is not involved with its campaign financing. Ducharme says he did lobby for a group of employers involved in workers compensation programs with the state, and the association included BIAW. But Ducharme says that was in 2000.

Evergreen Progress is bankrolled mainly by the national Democratic Governors Association, and labor unions. It’s an independent spending committee supporting Gregoire and opposing Rossi. The BIAW is financing its own third-party effort to support Rossi and oppose Gregoire.