Trump isn’t a conservative, particularly, at least not based on his past.
But he is a nationalist, and this time out, national sovereignty is the number one issue for many conservatives to the point that this issue “trumps” all others.
This is the point that many or most pundits miss, and this is the point that has tripped up almost every other candidate. National sovereignty is the number one issue for many people and its high on the list for most of the rest. Bush threw that issue away, as did Rubio, as did most of the other candidates. Trump seized it right out of the gate, and held on to it in the face of tremendous criticism even from GOP stalwarts. Thats why so many conservatives trust him on at least that issue if not on every issue. They have made a conscious decision that that issue is first.
Personaly I never use that term. Nationalist is a term of derision by the left wing...in Europe used against political enemies.. We tend to call someone who's total shtick is based on popular belief, a Populist. As far as nationalism goes, you can find that across the entire political spectrum in the US to one degree or another but more so on the political right and libertarians.. It really does not equate with patriotism, as many seem to think. It equates more to paleo conservatism.
Nationalism without constitutionalism and liberty is meaningless.