Greenwald today:

[T]here is very little political or media structure to Obama's Left that can or will criticize him, even when he moves far to what the Beltway calls the "center" or even the Right (i.e., when he adopts large chunks of the GOP position).  That situation is extremely bad -- both for the Left and for Obama.  It makes impossible what very well might be the apocryphal though still illuminating FDR anecdote:

FDR was, of course, a consummate political leader. In one situation, a group came to him urging specific actions in support of a cause in which they deeply believed. He replied: "I agree with you, I want to do it, now make me do it."

As Judis points out, Obama, on some issues, might move to the Right because he wants to.  In other cases, he will do so because he perceives that he has to, because the combination of the GOP/Blue-Dog-following-caucus/Beltway-media-mob might force him to.  Regardless of Obama's motives, the lack of a meaningful, potent movement on the Left to oppose that behavior ensures that it will continue without any resistance.  The lack of any independent political pressure from the Left ensures that Obama will be either content to ignore their views or will be forced to do so even when he doesn't want to.

Glenn leaves out one part of the dynamic: If you criticize Obama, or his enablers, be prepared for Deru kugi wa utareru.

Get prepared to be called a stalker, a bugfucker [half to admit I love that one], a racist, etc., by the usual suspects. Perhaps I should put together a rogue's gallery, at some point. Could be fun!

NOTE No, Dave, I'm not "stalking" you because I'm linking to you. Jeebus. And as Basement Angel points out, it might be better to reserve the term "stalking" for a real experience that terrorized women undergo, rather than appropriating it to describe the ego damage suffered by a teebee celebrity when some C lister calls bullshit on plain bullshit. And that, thank God, disposes of Sirota; now I can go back to not reading him.

UPDATE Style tweaks.