Born Norwich, New York, Campbell moved to Washington, D.C. after completing high school and began working for a succession of politicians, including for United States Secretary of Housing and Urban Development, Robert C. Weaver, as a clerk-stenographer from 1965 to 1967.

[1] In 1990, Campbell won election as Iowa's attorney general as a Democrat, defeating her Republican opponent, Ed Kelly.

On March 21, 1995, Bill Clinton appointed Campbell to head the United States Department of Justice's newly created Office on Violence Against Women.

[5] On March 2, 2000, President Clinton nominated Campbell to the Eighth Circuit vacancy created by the retirement of George Gardner Fagg.

[12] In the 2020 Democratic Party presidential primaries, Campbell endorsed former Vice President Joe Biden.