2016 Election Forecast | FiveThirtyEight
Trump sinks to rock bottom ...
According to their "polls plus" methodology, which takes into account the number of days left before the election, and the likelihood of vote-changing events within that time-frame, Trump is now at his lowest point ever. (20.4% chance of winning on Election Day.)
RCP's methodology is in general agreement. They say Trump has a 14% chance of winning, and they also place the current time at his lowest point ever.
By the way, the NBC/WSJ poll updated its results with another day of interviews on Monday, and they have revised the numbers to the following: Hillary up by 10 head-to-head, 9 in a four-way race. In other words, her lead has narrowed somewhat. That may indicate that Trump made some headway in the Sunday debate.
Other polls that include the weekend (but do not include Monday) show a widening gap between the candidates in a four-way race, but nowhere near nine points. Unfortunately, those results are confounded by the percentage of interviews which took place before the tape was released, so it may have been nine points over the weekend. It's just not possible to gain precise info from these results about the specific impact of the tape.