Editor’s note: A version of this essay was delivered at a symposium sponsored by The New Criterion on “The Kennedy Phenomenon” on November 19, 2013. Additional papers from the symposium will be published in future issues.

The Kennedy Assassination is not a whodunit. Cranks and conspiracy adherents aside, it’s clear that Oswald did it and did it alone. Nonetheless there is still a great mystery surrounding the Kennedy assassination—and I’m not referring to Jack Ruby. The mystery is this: Why is it that American liberals have been so unable to assimilate Oswald’s left-wing identity into their account of the assassination?