I do not believe the chances of Trump winning are high, but they are much higher than 0.005%
They are much higher than
1 A vs 19,999 Bs
Nate Silver's 538 puts the current odds at 52.4% Clinton, 47.5% Trump, the rest going to the House of the Representatives or the Courts to settle this out
http://projects.fivethirtyeight.com/2016-election-forecast/?ex_cid=mobilebar
Previously same guy in his model stated the chances of trump winning is about 20%. The link I gave has graphs and timelines of when the model says X vs Y.
Arguably the most important 3 states to watch in polls are North Carolina, Ohio, and Florida to see who is going to win Clinton or Trump.