Sen. Benjamin L. Cardin (D-Md.), right, talks to Senate colleagues. (Andrew Harrer/Bloomberg)

Maryland Lt. Gov. Anthony G. Brown (D) will pick up an endorsement of his gubernatorial bid on Monday from U.S. Sen. Benjamin L. Cardin (D-Md.), according to two people familiar with the planned announcement.

Cardin will become the latest high-profile Maryland Democrat to throw his support behind Brown in a primary next year that also includes Attorney General Douglas F. Gansler (D) and Del. Heather R. Mizeur (D-Montgomery).

The Brown campaign has advertised an event Monday morning in Baltimore at which it will make a “major announcement” about the campaign. The two people familiar with the announcement confirmed Sunday that Brown will be unveiling Cardin as his latest supporter. They requested anonymity because they are not authorized to speak for Cardin or the Brown campaign.

Cardin has been a fixture in Maryland politics since 1967, when he became a member of the House of Delegates. He was chosen by his colleagues in Annapolis as House Speaker in 1979, a position he held until his election to a Baltimore-area district in the U.S. House of Representatives in 1986. Cardin was first elected to the U.S. Senate in 2006.

Cardin’s colleague, Sen. Barbara A. Mikulski (D-Md.), has previously endorsed Brown to succeed Gov. Martin O’Malley (D). Other Brown endorsees include O’Malley, House Minority Whip Steny H. Hoyer (D-Md.) and both Maryland Senate President Thomas V. Mike Miller Jr. (D-Calvert) and House Speaker Michael E. Busch (D-Anne Arundel).

Gansler, who is trying to reboot his campaign after a rough start, has sought to downplay Brown’s endorsements, saying they reflect a race between a candidate favored by the Democratic establishment and one who will put the needs of voters first.