If you could settle the question with a national vote, there would be no doubt that a conspiracy killed John F. Kennedy. Two weeks after the shooting, a Gallup poll showed 52% of Americans blaming a force larger than Lee Harvey Oswald for the President's death. Half a century later, a new Gallup poll puts the number at 61%. Earlier this year an Associated Press survey said the number was 59%, while a Public Policy Polling effort said it was a more modest but still substantial 51%—not far at all from those initial results in 1963.
Those numbers may sound surprisingly high, but by other years' standards they're actually low. A decade ago, an ABC News poll had 70% of the population believing there was more than one man behind the slaying. When ABC posed the same question in 1983, the number was 80%. In 1994, the sociologist Ted Goertzel suggested that belief in a Kennedy conspiracy has "increased as the event became more distant." For a while it did, but then it reached a peak and started sinking.
So there are two trends that cry out to be explained here. Why are Kennedy-assassination theories still so popular, and why are they less popular than before?
For my answers to those questions, read the rest of the piece.