Courtesy of Think Progress:
With just a few weeks left until voters start casting their ballots, GOP nominee Donald Trump has finally cut a general election TV ad, which will air in Pennsylvania, Ohio, Florida, and North Carolina. One of the very first images in the 30-second ad shows a line of people waiting in line to vote, with a soundtrack of ominous music playing and the words “system rigged” emblazoned across the screen.
In the context of the last few weeks, amid Trump’s warnings of election rigging and potentially illegal exhortations for untrained supporters to help root out voter fraud, the message of the ad is clear. Trump, who is down in the polls (all of them), is encouraging his base to view a Clinton victory as illegitimate.
Gee that's helpful.
But of course Trump has to accuse Hillary of rigging the system because he is beginning to realize that he is about to lose this election to a woman, and his ego demands that people believe that she cheated somehow.
Essentially Trump would rather agitate his supporters into reacting with violence, and even perhaps foment a civil war, than to admit that he lost because of his own shortcomings and lack of ability.