Maryland Del. Heather R. Mizeur. (Karl Merton Ferron/Baltimore Sun Staff)

Del. Heather R. Mizeur (D-Montgomery) has won the endorsement of the Maryland chapter of the Sierra Club in her bid to become the state’s next governor.

The group is the first environmental organization to endorse in the competitive Democratic primary for governor, which includes two better-known and better-funded candidates: Lt. Gov. Anthony G. Brown and Attorney General Douglas F. Gansler.

“Delegate Mizeur is a true environmental champion who leads the fight to ensure that all Maryland families have access to clean water, healthy air and open spaces,” Josh Tulkin, state director of the Sierra Club’s Maryland chapter said in a statement. “Heather isn’t afraid to speak her mind and stand up to special interests.”

Mizeur said she was honored to have the support of a national group with 12,000 members in Maryland.

“The next governor will face tough environmental challenges, from eradicating dead zones in the Bay and boosting our alternative energy options, to protecting and sustaining our natural resources,” she said.

In the early stages of the governor’s race, Brown has dominated the endorsement process, winning the backing of far more fellow Democrats and liberal interest groups than his competitors.