MoveOn.org endorsed Democrat Darcy Burner on Monday for the open 1st district.

Of the approximately 19,000 members of the progressive grass-roots organization who live in the district, the more than half who participated in the endorsement vote chose Burner, a longtime liberal favorite.

The all-party primary is Aug. 7, and Burner is one of five Democrats running for the seat of former Rep. Jay Inslee (D). John Koster (R) and Larry Ishmael (I) are also running. The redrawn 1st is the most competitive district in the state, and one Democrat is likely to advance along with Koster. A few other candidates are running only in the coinciding special election to fill the final two months of Inslee’s term.

A week ago, the Service Employees International Union endorsed Suzan DelBene (D) for the seat. Gov. Christine Gregoire and Rep. Rick Larsen are also backing DelBene, who lost to Rep. Dave Reichert (R) in the 8th district in 2010. Burner lost to Reichert in 2006 and 2008, and Koster lost to Larsen in the 2nd district in 2000 and 2010.