The Republicans have shifted right, and the Democrats seem to have shifted to the right with them, overall. But the Democrats are a coalition. Always have been. The factions (along with the rough percentage of democratic voters who correspond to each faction)
Blue Dogs: 10%. Southern rural rightwingers in the wrong party. Social and economic conservatives. Would be Conservatives in any other country (and very right-wing ones at that.). Max Baucus, and Mary Landrieu, and others of the sort would fit in this category.
New Democrats: 30% Would be considered centrist here, though they'd be center-right in most other countries. Basically Clintonians. Economically pro-business and pro-welfare reform. Generally more socially liberal. While they're roughly 30% of Democratic voters, it would seem that at least half, if not more, (probably the latter) of Democratic officeholders are New Democrats. (or blue dogs). Would either be moderate conservatives or right-leaning Liberals in most countries. Some examples would include Hillary (and Bill) Clinton, Harry Reid, Andrew Cuomo, Mark Warner, and others.
Liberals: 15%. Would be considered left-liberal in other countries. Basically generic democrats. They are a bridge between the New Democrats/Blue Dogs and the Progressives. Usually socially liberal, and economically center to center-left. Usually pro-universal health care, mixed on labor, and plenty of them clash with labor on occasion. Also tend to be Greenie-ish. Open to cutting social security spending when they see it as "necessary." Essentially, they are a gray area that could be applied simply to democrats that aren't "progressive" or "New Democrats/Blue Dogs". Amy Klobuchar, Deval Patrick, and some others would fit in this group.
Progressives: 45% the type who would be seen as social democrats and possibly democratic socialist in other countries, though only a small few would dare openly call themselves social democrats, and certainly not socialist, since socialism has been demonized to an unbelievable degree in American society. Economically and socially left. While close to half of those who would identify as democrats would be considered progressive, only some legislators who identify with this ideology are elected. It's also quite rare for people who are considered "progressive" to actually be elected to executive office. While Barack Obama's roots may be in this faction, his 2008 campaign appeared to be more "liberal," and he has governed as a New Democrat. Russ Feingold, Denis Kucinich, Alan Grayson, Elizabeth Warren, Tammy Baldwin, etc. would be prime examples. I, for example, would be comfortable in this faction, but are too irked by the other factions too call myself a Democrat. Therefore, I count myself as an independent socialist/social democrat.
In the early 1960's, it would have been:
Progressive/Social Democrats: 55% with people like JFK and Adlai Stevenson, as well as others, with the war on poverty being crucial. Would've blended with the "liberals."
Southern White Conservatives: 30%. Segregationist racist bastards like George Wallace who ditched the Democrats for the Republicans later because they hated the Civil Rights Act of 1964. Those that remained might've evolved into the Blue Dogs.
Those that would become New Democrats: 15% There were plenty of pro-business folk in the Democratic Party at that point, but they didn't wield the influence that they do today.
I don't think that any of these catagories really apply to the Democratic minority voters. I doubt, for example, you could call the black and hispanics who voted for proposition 8 as progressives. They also aren't really in favor of welfare reform so new democrats are out, and no other catagory is large enough to hold them. All in all, I really think you overestimate the number of true leftists in the Democratic party.
