Last week, pollster Nate Silver was so confident in a Biden win that he suggested the only way Trump is reelected would be through a 'major polling error' or cheating.

Nate Silver @NateSilver538

If the polls aren't tightening since the debate—and with 62 million people having voted—we're sort of getting to the point where the only way Trump can win is with a major polling error, bigger than in 2016 (or if the election is stolen somehow).

@amuse @amuse

Nate Silver is spreading unfounded speculation that the only way Trump can win is to steal the election. This is irresponsible and will ensure a Trump victory isn’t accepted by Democrats.

This weekend, however, Silver shoehorned a giant caveat into weeks of confidently proclaiming a Biden win: Pennsylvania.

"Pennsylvania has not bumped up to a 7- or 8-point Biden lead like we see in Michigan and Wisconsin. It's 5 points," Silver told ABC's "This Week" (sporting a new 'battle beard') adding that if Trump were to win, "it would come down to Pennsylvania."

Silver then sets the expectation for an unfair vote, saying "Among the votes that were sent in by mail, there are some provisions about a naked ballot, a security envelope. That could make things more complicated. You could have the courts involved. You have some protests, looting in Philadelphia. There's lots of stuff going on."

And then, Silver says that if Biden doesn't win PA, he'll become the underdog.

"Maybe a lot of little things add up and Biden loses Pennsylvania by half a point, and then he doesn't quite pull off Arizona or North Carolina. He does have other options. ... But still, without Pennsylvania, then Biden becomes an underdog."

This Week @ThisWeekABC

Just days ahead of November 3, the @FiveThirtyEight presidential election forecast has Joe Biden with a 90 in 100 chance of winning the Electoral College.

@NateSilver538 breaks down the forecast: http://abcn.ws/3oEqgAy

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