William B. Ewald Jr., who was a White House speechwriter for Dwight D. Eisenhower and wrote several revisionist histories to help redeem the former president’s reputation, died on Monday at his home in Greenwich, Conn. He was 89.

The cause was respiratory failure, his son William B. Ewald III said.

The elder Mr. Ewald helped Eisenhower write a two-volume memoir of his presidency, “The White House Years: Mandate for Change, 1953-1956” and “Waging Peace, 1956-1961,” and after spending four years debriefing Eisenhower at his farm in Gettysburg, Pa., Mr. Ewald probably knew the particulars of his White House years as well as anyone.