Democratic gubernatorial candidates, from left, Lt. Gov. Anthony G. Brown, Rep. Heather R. Mizeur, and Attorney General Douglas F. Gansler chat after a debate in June. (AP Photo/Patrick Semansky)

The campaign of Maryland Democratic gubernatorial nominee Anthony G. Brown on Wednesday announced the endorsement of the Sierra Club, an environmental group that had sided with a rival candidate in the primary.

The Maryland chapter of the organization supported Del. Heather R. Mizeur (D-Montgomery), the third-place finisher in the June Democratic contest, calling her “a true environmental champion.”

“When it comes to the general election, of course, we have to reevaluate what the race looks like,” Betsy Johnson, the group’s political chairwoman, said in an interview Wednesday.

Johnson said the Sierra Club decided to back Brown, the state’s lieutenant governor, largely because of achievements during the past eight years under Gov. Martin O’Malley (D) and because of the knowledge of environmental issues shown by Brown’s running mate, Howard County Executive Ken Ulman (D).

“Anthony Brown has been part of the O’Malley-Brown administration, which has done good things for the environment,” Johnson said, citing efforts to clean up the Chesapeake Bay, bring clean energy jobs to Maryland and expand the use of wind and solar power. “We’re hopeful the Brown-Ulman administration will carry on the work of the O’Malley-Brown administration.”

Johnson also cited another factor in the group’s decision: Efforts to meet with Anne Arundel County businessman Larry Hogan, the Republican nominee, were unsuccessful.

“Larry Hogan didn’t give us any choice,” Johnson said.

Also Wednesday, Brown attended a unity rally in Waldorf with Democrats from Southern Maryland, including U.S. House Minority Whip Steny H. Hoyer (D-Md.), an early Brown supporter.