Bob brings up an excellent point today:
The retirement of Byron Dorgan is a solid example of why, in many cases, legislation is at the mercy of conservative-leaning states, and nothing the president can- or should do will change it.
With Dorgan out, it's very likely that a Republican will win that seat. If Ben Nelson were to resign, he'd probably be replaced by a Republican. Blanche Lincoln is likely to be replaced by a Republican. It goes without saying that those Republicans won't be very receptive to robust public options or passing the Obama agenda.
Progressive groups would be helped to remember one of the greatest quotes given by Tipp O’Neil, “all politics is local”. Let’s go with the example of Blanche Lincoln and Arkansas.
GovTrack ranks Lincoln as a moderate Democrat, something we all know. In 2008 Arkansas went for McCain by +7, so Arkansas is a red state. That pretty much means that Lincoln and Pryor are the most liberal we will get out of Arkansas, unless the state makes a dramatic shift to the left.
This brings us to the point of primaries. A lot of national organizations will be focusing on unseating Lincoln in the primary, a very possible feat, but at what costs? If we end up replacing Lincoln with a more liberal/progressive candidate, will they hold up against the general electorate, which is much more right leaning? Most likely not.
So where does this leave us?
Well Lincoln is out as the Democratic candidate and replaced with someone far more progressive, then we will lose a Senator that votes with the Democrats somewhere along the lines of 30-40% of the time. That will be replaced by a Republican who will vote with Democrats 0-10% of the time. In the long run we will lose.