When you now look back at the 2008 GOP presidential field, what is striking was its ideological diversity. You had someone who supported abortion rights (Rudy Giuliani), a candidate who had previously defended Roe v. Wade and embryonic stem-cell research (Mitt Romney), another person who backed comprehensive immigration reform (John McCain), and even another who opposed the Iraq war (Ron Paul). But four years later, no matter who ends up running, the 2012 GOP field will be much more homogeneous.Anyone spot the problem? First of all, the candidate who once was pro-choice and for stem-cell research is running again this time around, so that can't possibly be different. Then there's Ron Paul -- but Ron Paul may well run, and whether he does or not Gary Johnson is at least as heterodox in his views as Paul was.
Now, we'll have to see whether Jon Huntsman really runs, but his issue positions are at least as nonconforming as McCain's were in 2008 (of course, he's not apt to be a leading candidate, so that one isn't quite parallel).
Of course the real truth about this is that (Paul aside) the 2008 GOP contest wasn't a battle of contrasting versions of conservativism. Instead, those candidates who had once held unacceptable views on various issues mostly either converted, and hoped that their conversions would be judged sincere -- or downplayed their deviance, and hoped it would be ignored or forgiven.
Not that the Democrats in 2008 were any different. They just, for whatever reason, had a set of candidates with relatively long records of orthodoxy, so it didn't come up.
It is, in fact, still very possible that we'll see a true significant policy rift between GOP candidates this time around. It's possible that one of the major candidates will depart from feel-good sound bites (whether it's on immigration, or the budget, or foreign policy) and actually stake out a position that might help with GOP primary voters, but is highly risky with the November electorate. For example, a candidate might actually give a detailed spending cut plan -- a real one, not smoke and mirrors. (No, I don't expect it to be defense cuts). If a top-tier candidate runs on that, would the others have to match (and perhaps top) it? Would it be sufficient to just up the ante on the feel-good sound bite? What about if a major candidate runs on a policy of attacking Iran, or of withdrawing from Geneva? What happens then?