House Democratic Caucus Chairman Bob Menendez (N.J.) will endorse the presidential campaign of former Vermont Gov. Howard Dean although the specific timing of the announcement has not yet been set, according to Capitol Hill sources.

Neither Menendez’s office nor Dean’s campaign were available for comment.

Menendez’s backing provides a two-fold boost to Dean. First, it signals Dean’s continuing inroads in Washington where his 24 Congressional endorsements are now second only to Rep. Richard Gephardt’s (Mo.) 34. Dean’s Hill backers are privately predicting that the former governor will surpass Gephardt’s total early next year.

Menendez is the first member of the House or Senate Democratic leadership to get behind Dean. House Minority Leader Nancy Pelosi (Calif.), Minority Whip Steny Hoyer (Md.), Caucus Vice Chairman James Clyburn (S.C.) and Assistant Minority Leader John Spratt (S.C.) are all backing Gephardt. Former Minority Whip David Bonior (Mich.) will endorse Gephardt today at 2 p.m.

And, perhaps more important in the early primary process, Menendez is the highest ranking Hispanic ever in the House and could be a major asset for Dean in Feb. 3 primary states like New Mexico and Arizona.

As Dean has emerged as the prohibitive favorite for the Democratic nomination over the past month, he has also gained significant momentum in the Congressional endorsement game.

Dean’s campaign has pursued a strategy of announcing Congressional supporters in small groups at events in the Members’ home states rather than holding a single large event.

Earlier this week Dean picked up the endorsements of California Reps. Xavier Becerra, Lucille Roybal-Allard and Hilda Solis at an event in Los Angeles.

New Jersey Gov. Jim McGreevey (D) will endorse Dean tomorrow but knowledgeable sources indicated that Menendez will not offer his support then.