Ian Welsh noted it, in his observations on Netroots Nation convention in July 2010. As he explained it, one side sees Obama as little better than Bush, Part Deux, while the other side defends Obama as pragmatic.
This was never a stable divide. Each group forms a hypothesis, and revises its estimates, as new data emerge. More Obama was not going to confirm Democrats in their beliefs, in equal measure.
Digby notes the moving frontier on reaction Obama's Grand Bargain with the Republicans:
It appears that the Obama supporters in the political establishment have awakened to the fact that he really does want to enact a Grand Bargain and that it's highly likely that it will end up being a bad deal for Democrats.
Obama has an interesting political problem. On the one hand, he wants to serve the kleptocrats well enough that they do not turn to the Republican candidate in 2012. On the other, he is vulnerable to being deserted by his own Party. It is an asymmetric dilemma, because of "vote for the lesser evil" two-party system. Obama is actually aided with both the corporate center and its money, and with distressed Democrats, since both groups, for differing reasons, fear the worst from a crazy Republican.
Obama is likely to continue to do his best to serve the plutocracy, knowing that this keeps the smart money out of Republican politics, increasing the chances that the Republicans do the wild thang! Which, in turn, increases Obama's stranglehold on the Democrats, including the left of the Democratic Party, which has no alternative course of action, save to give up hope altogether.
Giving up hope might be the smart play.