Lise Van Susteren (search), a psychiatrist and sister of Fox News' Greta Van Susteren (search), plans to announce Thursday that she's seeking the Democratic nomination for the U.S. Senate.

Two well-known Democrats — former Rep. Kweisi Mfume (search) and Rep. Benjamin Cardin (search) — have already entered the race. On the Republican side, Lt. Gov. Michael Steele (search) is considering running for the seat that will open up with the retirement of Democrat Paul S. Sarbanes.

A news release issued Monday said Van Susteren will open her campaign with events in Baltimore and Bethesda. She will discuss the need to improve public schools and the health care system, and will challenge the Bush administration on the conduct of the war in Iraq, the release said.

Van Susteren, 54, is the mother of three teenagers and the wife of Jonathan Kempner, president and CEO of the Mortgage Banker's Association in Washington.