The Maryland State Education Association is supporting Sen. Brian E. Frosh for the Democratic nomination, adding the support of the state's largest teachers union to his list of labor endorsements.

The MSEA decided to back Frosh, a veteran Montgomery County lawmaker, at its spring representative assembly in Annapolis.

Frosh is running against Del. Jon Cardin of Baltimore County and Del. Aisha Braveboy of Prince George's County in the June 24 primary. Another large public sector union, AFSCME Council 3, previously endorsed Frosh.