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(CNN) —  

Former Montana Gov. Brian Schweitzer endorsed former Maryland Gov. Martin O’Malley, giving his Democratic colleague a boost as the Democratic field thinned out this week.

“I’m endorsing Martin for President today because I believe he is the candidate that best represents the future of our Party,” Schweitzer said in a statement. “Martin and I worked closely together as Democratic governors, and I saw firsthand how he didn’t just talk about his progressive values—he actually put them into action.”

Schweitzer, who was at one time considered a possible 2016 Democratic presidential contender, will also serve as the national co-chairman of O’Malley’s campaign.

The endorsement comes just hours after former Rhode Island Gov. Lincoln Chafee announced he was dropping his bid and a few days after former Virginia Sen. Jim Webb dropped his bid.