That phenomenon was seen in the former City of Toronto's 1980 mayoralty race. All the polls predicted that John Sewell would be re-elected Mayor by a solid margin. Even on election night, the networks declared him elected before all the votes were counted. To the great chagrin and embarrassment of the mainstream media, Sewell lost narrowly to Art Eggleton.  CBC et al. had to eat a heaping helping of crow and reverse their declaration of victory. The conclusion was that a lot of Torontonians had lied to the pollsters during the election campaign. Even if Trump doesn't win on November 8, the race is going to be much tighter than Hill's shills are predicting.