Last month! The month he turned the Republican National Convention into a Nuremberg Hate Fest. The month he attacked the parents of a War Hero as Muslim Traitors! The month he said he wouldn't abide by our NATO International Agreements!
His supporters do not care that Trump doesn't know why we don't drop nuclear bombs first, or that Trump doesn't know Russia has already invaded Ukraine or that Trump doesn't know we are already allied with Russia against ISIS.
They don't care because they don't know either, they're not stupid. They don't know because they have real life to worry about. And everyone in America (including me) thinks "Hey, I could do a better job than the idiots in Washington."
So the fact Trump doesn't know shit from shinola isn't a deal breaker.
And I don't think they support him because he is a racist. They support him because he "speaks the truth and sometimes that sounds racist." Just like manny liberals "speak the truth about Trump supporters and demean them." We justify this by saying, "hey it's not an insult if it is true."
If November 8th is a sunny, nice day, Hillary will win going away. If November 8th happens to be a shitty shitty weather day in Ohio, Pennsylvania and couple of other states, prepare for President Trump. His voters will come out, because they are tired of being ignored, put down and shut out of the system.
BY THE WAY
If the Republicans do repudiate him and withdraw their endorsement - that does nothing to diminish his appeal. In fact, for his most ardent base, that would probably actually help turn out. If the Republican Machine (infrastructure) was turned off, that would hurt. But Paul Ryan repudiating him will only help him.