The Sierra Club endorsed Del. Heather Mizeur in the race for governor Monday, the first major environmental group to back a candidate in the contest.

While Lt. Gov. Anthony Brown has dominated the endorsements in the  heated Democratic primary campaign, Mizeur has recently picked up some coveted backers, including the Sierra Club.

Mizeur, a Montgomery County Democrat, has also collected the backing from  women's groups, including EMILY'S list and the political action committee of the Maryland National Organization for Women.

“Heather isn't afraid to speak her mind and stand up to special interests," Josh Tulkin, state director of the Sierra Club Maryland Chapter, said in a statement.

Attorney General Douglas F. Gansler is also in the Democratic race to succeed Gov. Martin O'Malley, who is term-limited. The primary is June 24.