It occurs to me that Bernie Sanders is in a counterintuitive Catch-22 situation. His only actual chance to be the nominee is to convince a bunch of crooks (as he basically calls them) to switch their allegiance to him, and the only possible way to do that is to persuade them that Clinton can’t win. The only evidence he could ever produce to back up that claim are polls that show Clinton losing.
But a poll showing Clinton losing actually has the opposite effect of making everyone lose patience with him and really insist that he drop out and make nice.