A rank opportunist? McCain? Absolutely. However, political views do not exist in isolation, like a dot on a white board. Political views, both within individuals and within groups of individuals, exist on a spectrum, very much akin to the spectrum of light.
Using the visible light analogy, the political views of a majority of people generally occupy the green portion of the spectrum, sometimes shading a little to the cyan-light blue (center left) side and sometimes to the yellow-light orange (center right), depending on the issue.
Most politicians occupy that territory for obvious reasons. That's where most votes are to be found. So in that sense, they are all opportunists. To put it another way, they are all realists where their electoral self-interest is concerned. Libertarians also reside here and, depending on the issue, flip back and forth between light blue and light orange.
Totalitarianism is found on both the very far left and very far right ends of the spectrum, and extremists occupy the regions just inside either end. All of the other political viewpoints except anarchism fall somewhere in the blue-purple (mainstream left to far left) and orange-red (mainstream right to far right) parts of the spectrum.
I think most conservatives and right-wing populists occupy the yellow-orange to red part of the spectrum, just before it shades into dark red. The problem we have is that too many of us see conservatism as a dot on a white board rather than a spectrum. As a result, too many of us reject anyone we see as stepping off the conservative dot onto the white board. Problem is, the world doesn't work that way. Neither to flesh-and-blood human beings.