The mathematician and philosopher Laplace said that “the weight of evidence for an extraordinary claim must be proportioned to its strangeness.” That leaves to individual judgment whether or not one regards something as strange. Some might think the idea that Kennedy died for political reasons extraordinary, where others would regard a politically motivated assassination as entirely normal. Put briefly, the latter view holds there’s nothing extraordinary about political assassination.

Political leaders throughout history, if they have enemies, bet their lives. Almost all political leaders have enemies. They know that if things do not go the right way – if something goes amiss or they commit a serious error – they may be executed, assassinated, exiled, or removed from office in disgrace. People who operate in the political arena play for keeps. Political killings stand out in history not because they are rare, but because they spawn significant consequences. Historians often tie them to a characteristic type of political disintegration.

James Douglass’s account of Kennedy’s death only appears extraordinary because the Warren Commission had the first lick. The Commission’s report became the first widely accepted explanation of Kennedy’s death. It encompassed twenty-six volumes of carefully catalogued testimony and evidence. The chief justice of the Supreme Court blessed it. President Johnson accepted it at a presentation ceremony and photo opportunity. It had the seal of the United States government on its cover, just like the 9/11 Commission report. No wonder so many people at the time trusted its veracity.

If Douglass had published his account first, and prominent people had blessed his research, the idea that Lee Oswald killed Kennedy by himself would seem extraordinary. During the traumatic hours immediately after the murder, however, officials managed to fix Oswald’s guilt in people’s minds. Delivering the first apparently credible package of information confers a large advantage in this kind of situation. Because the official narrative influences perceptions and memories, because it defines the boundaries of acceptable belief, the early accounts shape political and social reality. You can recover from these presumptions and rhetorical disadvantages if you disbelieve the official account, but effective rebuttal requires considerable work.