I think originalism makes some sense as a theory -- text means what it means, and the mere fact that it's 200 years later can't change the text's meaning, right? So I think that at least some of the originalists are such not because it helps support their conservatism, but because they honestly believe it. I think J. Thomas fits into this category. But others (I'm looking at you, Scalia) seem to use originalism when it helps them get the result they want, and discard it when it doesn't help (I'm thinking Gonzalez v. Raich). I tend to prefer the somewhat conservative but more pragmatic O'Connor, personally, though part of me misses Brennan.
Side note: I was having a conversation about originalism with a friend, and said, "I think Scalia's philosophy makes sense in a vacuum." To which she replied, "I'd like to see Justice Scalia in a vacuum."