So many people have already added this and been answered. People are tired of the establishment, of candidates who don't do anything they promised and seemingly don't get anything done. A lot of people support the idea that the next president shouldn't be part of the establishment, so donald trump is getting support from those people as well. Others see the election of trump as a stepping stone of finally destroying the broken two party system we have in place.

Maybe say since he is financing his own campaign he isn't being bought by anyone, so he would be legitimately be for the people by the people.

Even if many of the things he says seem exaggerated, the wall, stopping Muslims from entering the countries until we figure everything out are already things that people support, not all republicans do, but the percentage that do is significant.

Also there are others who argue that absolutely nothing will change no matter which one of the real politicians is president so why not elect Donald's trump and see what he can do.

Political correctness has gone too far. Like the professor who was fired for refusing a students request to be referred to as a he and then a she depending on what mood they were in that day. People are tired of it, and willing to overlook some of the things he says because he is speaking his mind, a sign that he isn't afraid like all other politicians. If Any other election or even this one, without donald trump in it, had a candidate saying what he says it would most likely be political suicide.

Trump is viewed as a successful business man. He's had a bunch of bad businesses, but overall he is viewed as a success so I'm sure that also plays some roll.

Not the majority, but definitely some racist are supporting him.

Tl;Dr Basically he's pandering.