Ezra Klein asks why the Democratic party doesn't treat "unreliable" Democrats quite as badly* as the GOP hunts down "Republicans in Name Only" such as Arlen Specter.
True enough, but Ezra could have gone further: the real answer is that the Democratic party isn't as stupid, right now, as the Republican party. That is, it recognises that it's better to have an unreliable Democrat in Congress than the alternative - a Republican. Outside the GOP coccoon this could be seen as a matter of common sense; inside the coccoon, however, it's a different story. The GOP's problem isn't that there aren't more "good" conservatives in Congress, but that there are too few Republicans. Specter and Snowe and Collins aren't the problem; the GOP's virtual elimination from much of the north-east is.“
There are few consequences to being a Blue Dog Democrat. Labor doesn't come into your district and fund a challenger who attacks your votes to cut entitlement spending. Business interests are more likely to donate to your campaign. You have a badge of independence from party which is useful both when dealing with the media and when dealing with voters. Your vote matters more because it's less reliable. And the Democratic Party infrastructure itself is fundamentally sympathetic to your plight: Democrats from marginal districts, they agree, have to be a bit more conservative. And we have to protect them. Numbers matter. There's a difference in priorities here: Liberals tend to prioritize the number of seats they have in Congress, conservatives are more protective of the purity of those in power. One emphasizes the importance of placing its allies in government and the other polices its own ideological atmosphere.
*Joe Lieberman is an obvious exception.Then again, Lieberman campaigned for the Republican party's nominee, not Barack Obama. Even so, while Sanctimonious Joe may not have been forgiven, nor has he been cast into the wilderness.