Washington | For years, as the government has declassified and published documents related — some very tenuously — to the assassination of US president John F. Kennedy, the assumption expressed by conspiracy theorists and some historians was that anything still being withheld could be big.

That assumption led some of President Donald Trump’s allies, including Kennedy’s nephew Robert F. Kennedy jnr, who is now the nation’s top health official, to push him to release the final tranche of files from the Kennedy archives, believing they might reveal damning evidence: namely, that Kennedy was not assassinated by a lone gunman in Dallas.