His base is so deluded that they believe he is "center-right", but normal people know he is going to way too far to the left.
And their caterwauling is very much noticed by the indies as is their gravitational exertion on Obama.
They're the reason the train jumped the tracks in the first place. After 1994 Clinton tacked to the right but Obama can't afford that because the lefties have so much emotional energy invested in him and are already screaming he's too far right, as you noted.
Clinton was allowed to to tack right because the liberals understood the consequences and allowed him to hold the line against Newt.
And Clinton was far more competent a politician.
Obama's sheltered life left him without the skills to contend with a resurgent opposition and a restless base because he never had to contend for anything. Every job he ever held was created and handed to him, i.e. the Chicago machine getting him elected, being groomed as Bill Ayers' cabana boy. He's pissed off the center and the right too much to recover. He can either cater to his base and die a noble, flaming death at the polls or announce he's going out like LBJ.