WOMEN VOTERS &OCTOBER SURPRISE

With the Election Day less than three weeks away and early voting already underway in many battleground states, the final debate is one of the candidates' last chances to get in front of millions of viewers and sway their minds.

"Clinton will criticize Trump's issue positions that have been outrageous and/or showed his incompetence," Prof. Shapiro said.

She will also open fire on Trump over a series of allegations of sexual assault in the wake of the exposure of a lewd 2005 tape in which Trump bragged in obscene languages about forcing himself on women sexually.

Despite scandals ranging from allegations of mafia ties to exploitative business dealings, and to racist and sexist comments, Trump, a reality TV star who has never been elected to public office, forced his way through the Republican primaries and ran, for a time, neck and neck with Clinton in national polls.

However, the bombshell of the vulgar tape dropped before the second presidential debate roiled his already momentum-stalling campaign and the deeply-divided Republican Party.

Despite Trump's insistence the comments were "locker room talk," a number of women have stepped forward to claim that they were assaulted by the Republican nominee, who denied their accusations.

The tape scandal built on growing questions about Trump's character since the first debate, including post-debate comments that personally attacked the 1996 Miss Universe winner Alicia Machado, Prof. Robertson said.

"The tape seemed to verify the worst fear of people, especially women, that Trump did not understand that his conduct was inappropriate and opened him to charges that he had sexually assaulted women," he added.

Prof. Shapiro believed that the scandal with deeper and festering self-inflicted wounds "will be very big in mobilizing women voters, especially better education ones, to support Hillary."

"Also in causing at least a small percentage of normally Republican voters to not vote for him -- though they are not likely to vote for Hillary, so that they might vote for a third party candidate or not vote for president; or not vote at all," he predicted.

With the polls tipping heavily in favor of Clinton, "Trump no longer has any influence over the outcome of the election. There is no new strategy he can pursue to win the election," Prof. Robertson said.

To win the required 270 Electoral College votes to the presidency, Trump needs Clinton to make a fatal mistake or an event or revelation that wrecks her chances of winning, he said.

"Every day, an October Surprise is less likely and an October surprise would have to be bigger and bigger to get attention. It is increasingly difficult to think of an event or revelation that would eliminate Clinton's growing lead in the Electoral College," he said.