"I'm not a member of any organized party. I'm a Democrat." - Will Rogers.
It's funny because it's true. And the reason it's true is because the Democrats have long been a party made up of sometimes disparate coalitions of interest groups. It's why the Republicans often get traction out of the "party of special interests" charge. Of course one person's illegitimate "special" interest is another person's vital political imperative. And it is also true that the bigger a party gets the more diverse these interests are likely to become. Hopefully these diverse interests won't be directly contradictory too often but there are going to understandable differences of priority and emphasis.
When the Republican party started to get really big in the 1980s, 1990s and early 2000s, they started to include more diverse groups of people. The old Republican party had its factions. There were moderate small business advocates from the Midwest (like Ford and Dole), libertarians from the far west (like Goldwater), and progressive liberals from the north east (like Rockefeller). To this group, Nixon then Reagan and finally Bush II added Southern white populists and Protestant fundamentalists (like Thurmond, Lott, Bush etc) many of who used to be Democrats. This latter group has been especially successful at taking over the GOP. They have driven out most of the north eastern liberals and the Club For Growth is going after the moderates now too (see earlier thread). The result is a party increasingly isolated both geographically and ideologically but at least they have ideological conformity.
So what does this have to do with the Democrats? The 2006 and 2008 elections have made the Democratic party bigger than its been since the 1970s. It's also more diverse than its been since then. There are some improvements however. The social reactionaries and conservative populists from the South are not back. But there are increasing numbers of moderately pro-business Democrats and even a handful of Western libertarians.
Why am I bringing this up? Because there is a risk that the Democrats could develop their own version of the Club For Growth problem. The anonymous comment expressing outrage that Obama hasn't gone far enough on a series of his/her high priority policies and saying that Obama is no better than McCain is the kind of person that would start such a Club For Growth organization. These are people like the Naderite folks that voted against Gore and stuck us with George W. Bush in the name of purifying the Democratic party.
The Democratic party has an opportunity to become the party of pragmatic good government. But it cannot do that if the left wing of the party is allowed to impose an uncompromising vision of what it means to be a Democrat. To be successful the Democratic party must find a way to keep people like "Anonymous" in check. This doesn't mean allowing people like Lieberman to get away with campaigning for the other party. It does mean that if Democrats - like the Obama White House or the leadership in Congress - put some things off or compromise out of political expediency, the party should seriously consider not being outraged about it.