In politics, reality is often not what is, nor what ought to be, but what's thought to be. When Bob Herbert, perhaps the most astute crystallizer and propagator of orthodox Democratic opinion -- I mean that as a compliment -- accuses Obama of "lurching right when it suits him," and "zigging with the kind of reckless abandon that’s guaranteed to cause disillusion, if not whiplash," Obama has a perception problem that a few speeches blaming the media is not going to solve.
The key conflict is not whether Obama flip-flopped. In general, where most people see him changing his mind, I see Obama as driven by his own instinctive need to re-evaluate what he knows and does not know, his preference for consensus over conflict, his ability to balance competing values, and his assessment of the politics of the possible. These can be attractive traits.
There's not a binary relationship between flip-flopping and consistency. Voters expect candidates to change their approaches as facts and premises change, and we all -- voters, the media -- sense intuitively when a politician tries to evolve the method of arriving at a principle without admitting an evolution -- and especially when the politician righteously denies what everyone can see, plain as day.
Of course Obama is changing his emphasis as facts on the ground change in Iraq; this is not inconsistency; this is acknowledging reality.
But to subsequently insist that Obama is saying the exact same thing with the exact same tone and the exact same emphasis ON EVERY ISSUE as reality changes, and as different set of facts out themselves -- that's what strikes a discordant note. It's does not seem rational. It does not comport with the way voters and the media experience what Obama says. Andrew Sullivan, who does not buy the premise that Obama is changing his mind, points out that maybe it's healthy for Obama to face sustained skepticism. Just because some folks at Chicago Center can't figure out why the press and some folks on the left don't quite understand Obama does not mean that Obama isn't doing everything he can to be understood.
NB: If Obama is somehow triangulating or moving to the center, there's no evidence to prove that's it's been successful or not, and probably there won't be, outside of the anecdotal evidence of focus groups and the relative change over time in various attributes that people ascribe to Obama. The broader danger, which I know that Obama's advisers understand, is precisely, as Markos Moutlisas writes, that he's "now acting like every other politician. For those who thought he was something 'new' and 'different', fact is, he's behaving like every other politician before him."