He acts on what he believes in, even though I generally disagree with him. That's why he doesn't care if the POOTUS is in the same party, and that's something I can very much respect. I've usually always referred to stuff like this in that I "like them as a person" with politics, but respect is a better way to describe it. I disagree with McCain, but I respect him. I disagree with Trump, and do not respect him.
Though I do agree with T$ that McCain really needs to retire. Very soon.