The basic answer to your questions is that the Democrats won the last election by a slim margin, and in many districts they took seats from Republicans by running candidates that ran toward the center, not to the far left. They attacked Republicans on corruption, vice, and other issues that struck chords with the average voter. Look at the Republicans that were brought down by Democratic attacks, and what the attacks involved--things that normally make Republicans angry, not Democrats.

The Moveon.org/Counterpunch wing of the party is, to put it bluntly, mostly nuts. The Democrats are trying desperately to appease and quiet them while at the same time not alienating the vast number of moderate voters they need to win elections. You can see a lot of this interplay in the Hillary campaign.

This is why there is no "get out of Iraq today" bill from Congress. This is why only a few leftist nutballs in the House from safe districts are talking impeachment. This is why Kucinich is not going to be the next Democratic candidate for President.