Dorothy Cotton, a confidante of the Rev. Dr. Martin Luther King Jr. who was the only woman in his inner circle of aides, marched in perilous civil rights demonstrations and was a driving force in getting Southern black people to vote, died on June 10 at a retirement home in Ithaca, N.Y. She was 88.

A friend, Bonnie Harrison, confirmed the death but did not give a cause.

A warm presence who occasionally sang spirituals to ease tensions at demonstrations, Ms. Cotton was the director of education for Dr. King’s Southern Christian Leadership Conference; typed his “I Have a Dream” speech in a hotel room in Washington in 1963; traveled with him when he went to Oslo the next year to receive the Nobel Peace Prize; and was staying in a Memphis motel room next to his until hours before his assassination in 1968.

“She was always an equal partner with Ralph, Andy, Jesse and Hosea,” the King scholar David Garrow said in a telephone interview, referring to the King lieutenants the Rev. Ralph D. Abernathy, Andrew Young, the Rev. Jesse Jackson and Hosea Williams. “She was so valuable and helpful to Doc.”

Ms. Cotton was fearless in her adherence to Dr. King’s preachings about nonviolence, faced Ku Klux Klansman in civil rights demonstrations and was left with a lasting injury after being attacked at a protest in Florida.