Democratic Rep. Donna Edwards of Maryland intends to join the race to replace retiring Sen. Barbara Mikulski, hoping to become the first African-American elected to the Senate from her state, according to officials familiar with her plans.
Edwards would become the second member of the state's House delegation to announce her intentions to run for the Senate. Democratic Rep. Chris Van Hollen joined the race last week.
No Republican has yet stepped forward to run for the seat in the Democratic state.
A formal announcement is expected in the near future by Edwards, 56 and serving her fourth full term in the House. The officials who disclosed her plans did so on condition of anonymity because the officials were not authorized to speak on the record before a formal announcement.
Edwards and Van Hollen both represent portions of the Washington, D.C., suburbs. Her district includes Prince George's County and has an African-American majority. Van Hollen represents adjoining Montgomery County, which is heavily white.
Edwards is expected to have strong support among progressives, while Van Hollen, with close ties to the leadership, is a prominent party spokesman in the House on economic issues.
A number of other Democrats also are exploring the race, including several other House members. Baltimore Mayor Stephanie Rawlings-Blake told MSNBC's "Morning Joe" on Monday that she would take a look at running, saying that Mikulski was "like having a Baltimore girl in the Senate."
"That very aggressive, unapologetic leadership style is needed in Washington, D.C., and I'm not afraid to tackle big issues," Rawlings-Blake said.
Mikulski first won her seat in 1986, and her retirement creates a rare open Senate seat in her state. She became the second Senate Democrat to announce she will step down. Sen. Barbara Boxer, D-Calif., has also said she intends to retire at the end of her term.
Among Republicans, Sen. David Vitter, R-La., will run for governor instead of seeking a third Senate term.
Republicans hold 54 seats in the Senate. Democrats and independents aligned with them control 46, meaning they must gain at least five in next year's elections to be assured of winning a majority.