BALTIMORE (AP) — Maryland Attorney General Brian Frosh has endorsed Democratic Rep. Chris Van Hollen for Senate.

Frosh announced the endorsement Friday. It comes two days after Van Hollen became the first person to say he will run for the seat now held by Sen. Barbara Mikulski. She announced Monday she would not seek re-election in 2016.

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Frosh says Van Hollen was a tenacious partner in efforts in the state Legislature to protect natural resources and pass common sense gun-control legislation. Frosh also says Van Hollen has been at the forefront of the nation’s most critical debates.

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Many members of Maryland’s congressional delegation have expressed interest in the open seat, though Van Hollen is the first to say he is running for it.

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