Who knows? Trump's politics of insinuation

One of Donald Trump’s favorite expressions is “who knows,” as in “Mrs. Kahn seems to have been prevented from speaking by her husband and her religion, who knows?” or “Hilary Clinton seems to be ill and lack stamina, who knows?” or (in reference to the charge that Putin is trying to influence the election), “Maybe the Democrats are putting that out, who knows?” or (and this goes back a while), “Barack Obama may not be a genuine American citizen, who knows?”

“Who knows?” is a question that can be inflected in several ways. It could be a straightforward request for information: “None of us is sure about this, so let’s ask someone who knows.” Or it could be an admission of defeat, a throwing up of the hands: “It would be good if there were a clear resolution to this controversy, but I don’t see one, so who knows?” Or it could be a maneuver that allows a speaker simultaneously to say something and avoid responsibility for it: “Some people are saying this, others are not, but who knows?”