Will Wilkinson, as is often the case, nearly made me fall out of my chair with this post. Money quote:
But simply dismissing the other team’s claims to moral conviction is way too convenient. It turns out that the Democratic party is also run by very, very wealthy people and interests. It also strikes me as lazy to assume that because the GOP isn’t beholden to various interest groups that claim to represent the working classes in the way the Democrats are, then the people with real power in the Republican party ipso facto have no sincere moral interest in the welfare of the working class. Yes, politics is a game of interests and coalitions. But coalitions often form around moral values. And people, even politicians, are moral beings and generally conceive of their interests in moralized terms.
This about hits it out of the park. I've said before that political coalitions tend to form around one or two umbrella BIG issues.* In the Republican Party right now, the BIG issue is quite clearly "national security" broadly defined. On the Dem side, though, the unifying issue is much more difficult to define. Probably the closest thing to a unifying issue is health care, but that is simply too specific an issue under which to form a broad coalition. Perhaps the party of the "little guy"? Not likely - as Wilkinson points out, the "little guy" is no more likely to be a Democrat than a Republican. On the whole, it's more likely that the Dem coalition is really now a coalition primarily united by several frequently overlapping, but far from mutually inclusive, sets of moral values: for instance, civil liberties (including civil rights), a less-aggressive foreign policy, and environmentalism.
I'd argue that the fact that coalition members on the Dem side do not all prioritize these moral values the same way gives rise to a party whose politicians are much more likely to lack discipline and unity as the politicians try to be all things to all coalition members. I'd also argue that the Dems have largely lacked a truly unifying umbrella issue since at least the end of the Cold War, maybe longer; the end of the Cold War had a similar effect on the Republican coalition, but the Contract for America cobbled it together again for a few years until 9/11 made national security THE unifying moral value for Republicans.
In any event, the nature of political coalitions is that they result in some very inconsistent policy-making (aka "pu-pu platter partisanship") while coalition members wind up honestly believing that the coalition's preferred policies are all completely consistent with, even necessary to, furthering the coalition's core moral values.
*These aren't issues upon which virtually every coalition member agrees, but rather are fundamental moral imperatives that serve to rally people into the coalition.