The cause was complications of neuro-Behcet’s disease, an inflammatory condition, his son Samuel said.
The title of Mr. Leiken’s unfinished memoir reflected the frustration of his fickle ideological soul mates, first liberals and later conservatives, who had assumed that once he embraced their orthodoxy he would never challenge it.
The book was to be called “How I Lost All My Friends.” That was an overstatement, of course, because as his positions evolved, Mr. Leiken (pronounced LAY-kin) also gained new supporters.
“He was a rare original thinker who based his conclusions on a wealth of research that forced others — even others with very different perspectives — to take his views seriously,” said Dimitri K. Simes, president of the Center for the National Interest, which was established in Washington in 1994 by former President Richard M. Nixon as a nonpartisan foreign policy research and advocacy group.
Pigeonholed as a leftist after teaching English at a labor union center in Mexico and promoting racial integration during Boston’s school busing crisis in the 1970s, Mr. Leiken drew the scorn of fellow liberals in 1984 when, in an article in The New Republic, he accused the Sandinista government of corruption and repression. Officials with the administration of President Ronald Reagan had claimed that the government was verging toward pro-Soviet totalitarian socialism.