It is worth noting that Obama is a Chicago Pol.
Chicago -- as in the system governed by Dick Daley and the other bare knuckled brawlers of midwestern politics.
We don't pull punches here, we don't play nice, and fundementally, we don't sell well on the rest of the country.
Those who come out of Chicago and succeed nationally (alla Dick Durbin, and Barack Obama) have mastered to one degree or another, the ability to smile at the crowds while your allies are poisoning your opposition.
Dick Durbin is the Senate Majority Whip -- his job is to beat senate democrats into line and count the votes. Obama is the President, his job is mainly to say no to congress, to speak broadly of positive things to the citizenry, and to maintain a steady hand restraining the military's desire to solve all problems with guns.
Right now they're beating on the progressive side of the caucus, because us lefty liberal types are traditionally easy to move. If we hold out, they will beat the "centrists" into line. They're Chicago Pols, they know how to do it, they're just waiting for us to force their hand.