Sen. Barbara A. Mikulski (D-Md.) attivess for a closed hearing on Syria earlier this month in Washington. (Photo Jim Watson/Getty Images).

Sen. Barbara A. Mikulski (D-Md.) announced Sunday that Lt. Gov. Anthony G. Brown (D) is “my choice” to be Maryland’s next governor, saying she felt strongly enough about it to get involved in a Democratic primary, which is unusual for her.

“I don’t make this endorsement lightly,” Mikulski said at a Brown campaign rally in Silver Spring that drew about 25o people. “I’m ready to get into it.”

Mikulski called Brown “a man of honor and a man of commitment,” and she said that Brown and his running mate, Howard County Executive Ken Ulman (D), have “the right stuff for the right time to do the right job that we need to have done.”

The rally was held in the home county of Brown’s two 2014 Democratic primary opponents, and it came just two days before Attorney General Douglas F. Gansler (D) plans to formally announce his campaign for governor in Rockville. That event Tuesday is the first of 17 stops that Gansler has planned for his announcement tour.

Del. Heather R. Mizeur (D-Montgomery) also is seeking the nomination in the June primary.

Word of Mikulski’s endorsement leaked last week. She became the latest high-profile Democratic to throw support behind Brown in the race to succeed Gov. Martin O’Malley (D).

Reps. Elijah Cummings (D-Md.) and Donna F. Edwards (D-Md.), both of whom have previously endorsed Brown, appeared on stage with Mikulski at Sunday’s event.

Other leading Democrats who have endorsed Brown include O’Malley, House Minority Whip Steny H. Hoyer (Md.) and state Sen. President Thomas V. Mike Miller Jr. (D-Calvert).

Mikulski on Sunday praised the work Brown has done in Annapolis, including on veterans issues and domestic violence prevention, as well as Maryland’s implementation of the Affordable Care Act.

“He is willing to tackle the tough issues,” Mikulski said.