The only people he's "alienated" within the Democratic party are the far, far left. What gets me is the people who claim Obama is "super liberal" or "socialist" or "far, far left".....when he's actually closer to center. These people wouldn't know what real "socialist" or "far, far left" politician was if it bit them in the taint. This country will never have someone that far left or conversely, someone far to right in the White House. It'll never happen. You run on the left, you govern from the center. The same applies to a Republican; you run from the right, you govern from the center. The majority of Americans consider themselves centrist/moderate/Independents and governing from either end will get you nowhere. The problem with the far left in this country is they thought Obama would govern from there, and he can't. Not if he expects a more center-left Congress to pass anything.
I truly feel the more moderate Dems, such as myself, haven't gone anywhere.