It seems to me that Kevin Drum is missing the obvious as he puzzles over what Barack Obama could be claiming to represent when he says he represents "real change." The implication of the claim, obviously, is that while Republicans offer stasis and he offers "real change" his opponent, Hillary Clinton, must offer "fake change."
I think the relevant idea here isn't "an end to polarization" nearly so much as it is an end to what Obama has referred to as "the smallness of our politics." In this frame, partisanship isn't being contrasted to finer-grained efforts to find compromise nearly so much as it's being contrasted to the pursuit of broad thematic goals rather than politics as trench warfare in which the fighting is fierce but nothing ever happens.
On a symbolic level, this is clear enough. It would be fairly ridiculous for George H.W. Bush to be elected president in 1988, beaten by Bill Clinton in 1992, Clinton succeeded by Bush's son in 2000, and Bush the Younger succeeded by Clinton's wife in 2008. And yet this seems like a very probably outcome. It's as if the two rival claimants to the throne could just settle their feud by having Hillary Clinton marry George P. Bush and unite the warring clans.
What does the difference mean in practice? Obama's people speak of a distinction between transactional and transformational politics, with their guy in the latter camp. But, again, what's the upshot? Sometimes, it may mean that Clinton would be to Obama's left insofar as she seems more eager to uncritically embrace public sector unions as a vital element of her minimum winning coalition. Other times, it may mean that Clinton is to Obama's right insofar as she also seems more eager to uncritically court groups like AIPAC and CANF when framing her foreign policy. Less partisan in this sense doesn't necessarily mean more "centrist" it means bigger and broader. The incompetence dodge critique of the Bush foreign policy is a perfect example of a position that's partisan to the exclusion of ideology or substance, just a bare assertion that Democrats could make all the same ideas turn out to be good ideas.
The problem for Obama is that the Democratic nomination process -- and especially the Iowa Caucus -- is a very transactional endeavor. And Obama doesn't want to be the high-minded candidate who earns praise and then loses. And to his people, that means he needs to win Iowa, which means putting this message forth so quietly that one begins to wonder if one isn't simply imagining things.