Donald Trump is a populist.
On the political spectrum, he is a defensive nationalist.
He wants to isolate the US from those he sees would cause harm.
Chinese trade
Mexican illegal immigration
Islamic terrorism
This is part of the secret to Trump's success. Seen in these terms, he wants things everyone can agree with, and makes them top priorities. The Democrats are in a position where they appear to be more concerned with not appearing to be racist and xenophobic then about the safety of ordinary Americans. A party that comes off this way will have trouble when push comes to shove.
Agreed. If you focus on two or three core issues that everyone can agree with ("It's the economy, stupid" being the classic example), you've at least got a chance. Trump is running on what many believe to be vital: securing the border, defeating Islamic terrorism, and looking out for American trade interests. That's his focus, in a nutshell.
We'll see whether those on the left can make the charges of Trump being a racist, xenophobe, and misogynist really stick; I suspect many will consider these accusations to be political noise, and will focus on the issues and a candidate's approach to addressing those issues, and in so doing, will find Tump to be an interesting candidate worthy of consideration.