Trump isn't running on any policies. Most people supporting him don't care what he thinks about budget policy, economic policy, tax policy, college debt, health care issues, wage policy, education policy, etc, etc.
Trump is running on hate. That's it. He declared it the instant he declared his candidacy. Racial / immigrant hate first and foremost, but as his campaign picked up steam and so did Hillary's, he picked up Hillary/Democrat haters. And let's not forget Obama haters - he's one himself, and that's why he's running.
Some of his supporters are on his side just because he's Republican and would sign bills that a Republican Congress writes, whatever those are (repeal Obamacare, cut off social programs, re-litigate gay marriage, etc). But of course, a lot of the support for mainstay Republican issues are hate-based to start with.
I suppose it would be more fitting if Trump being caught on camera using racial slurs were the tipping point. But open sexism will do. If, in fact, it does. I believe he'll lose, but I'm not convinced, only hoping, that this will make him lose big(ly).