Maryland Lt. Governor Anthony Brown speaks to supporters as he kicks off his campaign for governor at Prince George's Community College in May. (AP Photo/Jose Luis Magana)

Baltimore Mayor Stephanie Rawlings-Blake (D) will offer her endorsement Monday of Lt. Gov. Anthony G. Brown (D) as Maryland’s next governor, according to several people familiar with her plans.

The event, planned at a bakery in Baltimore, is intended to build on Brown’s early momentum in the race, which he officially entered in May, well ahead of his expected Democratic primary rivals.

Rawlings-Blake has signaled her support for Brown previously, but Monday will mark the first time she has offered a formal endorsement in the 2014 contest, the sources said. They requested anonymity because they are not authorized to speak for Brown.

Brown’s campaign issued an advisory Sunday advertising a “major endorsement” at Monday’s event, but would not confirm Rawlings-Blake would be offering it.

Brown’s chief Democratic rival, Attorney General Douglas F. Gansler (D), is expected to make his bid for governor official in September. Del. Heather R. Mizeur (D-Montgomery) , who is also expected to run, could announce as early as July. Rep. C.A. Dutch Ruppersberger (D-Md.) is also considering the race.

Brown, meanwhile, has already named a running mate — Howard County Executive Ken Ulman (D) — and rolled out several other endorsements. Those include Gov. Martin O’Malley (D), Reps. Elijah Cummings (D-Md.) and Donna Edwards (D-Md.) and 70 elected municipal officials.

Unless Ruppersberger runs, there is no likely to be a Baltimore-area candidate in the Democratic gubernatorial primary, raising the value of endorsements from officials in the region.

Correction: earlier versions of this article gave an incorrect party affiliation for Baltimore Mayor Stephanie Rawlings-Blake (D).