We just saw it here, and now its happening in the States as well.
Its the perception by journalists and opinion pundits that they "know" where the general public is at, and therefore that they can just pull voting predictions out of their ass -- instead of, you know, actually doing some research into what people are thinking and what they want their government to do.
In Canada, Prime Minister Trudeau was being written off by the press even before the blackface scandal knocked the Liberals off-message. But it was clear, even way back in August, that while people across the country were somewhat disappointed in some of the things that the Trudeau government had done (pipelines!) or had not done (pipelines!) we weren't all going to switch our vote to Conservative or NDP without a good reason.
Scheer and Singh tried throughout the campaign to give Canadians that good reason to switch their votes, but as the weeks went by it was pretty clear they were not making their case. Singh kept changing his mind and his message, thus confirming what everyone already thought -- a nice guy who is maybe in over his head. Scheer presented us with the spectacle of a leader who actively sandbagged his own campaign week after week, through his clumsy responses to problems - he couldn't defend women or LBGT, he couldn't figure out how to handle the American and insurance broker scandals, he started lying about his opponents, and finally he let the Con backroom boys dictate his non-response to the Kinsella scandal. It was a display of ineptitude unparalleled in recent Canadian politics -- and considering what we Liberals saw with Ignatief and Dion, that's saying something! Bernier and May seemed to be regarded by the media as potential giant-killers, but neither got any traction; it was Blanchet, ignored by the English-speaking media, who actually denied Trudeau a second majority.
In the States, I keep seeing Biden now being written off in the same way Trudeau was -- yet actually the nomination still remains his to lose. Biden is winning, or close to winning,
in all of the national polls. While Warren is making strides, she fell into the trap of saying she would raise taxes to pay for healthcare -- of course that's the only way to pay for it, but Americans are absolutely pathological about taxes -- and she may not be able to overcome this mistake. While I love Warren, and there's lots to like about most of the other Democratic candidates too, I do believe that incumbency in the States provides so many advantages that only Biden can achieve the national stature and the "back to normal" vibe to bring out the 70 million voters he will need to beat Trump.