Makes sense after the banner year that Obama’s had. Wait, what?

Let’s keep this in perspective: The new high for self-identified liberals is 23 percent. The low for the other two groups is 34 percent for moderates, also in 2013, and 37 percent for conservatives in 2007-08. For various political and historical reasons, “liberal” still retains a stigma. Even so, the trend lines are interesting. Here’s how Democrats, specifically, have self-identified over the past 10 years:

No mystery what happened there. Opposition to Iraq began on the left and as it grew more mainstream among Democrats the number of Dems who were willing to self-identify as leftists also grew. Taking back the House in ’06 and winning the White House in ’08 cemented the gains — although it’s fascinating to see no further immediate rise after the financial crisis. What’s murkier to me is the new boost “liberal” has gotten over the past two years. The easy explanation is that O’s reelection campaign, especially the class warfare and “war on women” elements, further nudged some Dems into identifying as lefties, but don’t forget that lefties themselves grumble about O’s alleged centrism. I’m not so sure the recent spike is an Obama thing as much as it is a reaction to broader political trends — ideological polarization, a stronger lefty grassroots movement online inspired by people like Elizabeth Warren and Bill de Blasio, and just sheer temporal distance from the 60s and 70s when “liberal” became a four-letter word in the first place. Michael Barone has a theory that one big reason for partisan bitterness these days is that the parties are more competitive with each other than they typically have been in other eras. Usually one dominates; as it is, in the past six years, we’ve had two huge victories by Obama sandwiching a massive conservative-driven Republican landslide in the House. If Barone’s right, it’s no surprise that members of each party are identifying more with their ideologues than with the squishes in the middle. Case in point, here’s the drift among Republicans:

As is true among Democrats, moderates have lost exactly eight points to people who self-identify more ideologically. As is not true of Democrats, though, the number of people on the opposite pole has remained flat. Self-identified “liberal” Republicans have dropped just a point since 2000, but “conservative” Democrats have dropped six points, which helps explain why “liberal” Democrats are up 14 points overall. What you’ve got here, I think, are a whole bunch of moderate Democrats suddenly describing themselves as “liberal” and a smaller bunch of conservative Dems redefining themselves as moderates. The whole party’s shifting left.

Update: Needless to say, the consistency in Republicans’ willingness to identify as conservative versus the big shift among Democrats is striking. Even before Dubya, a heavy majority of GOPers identified ideologically. That’s a legacy of Reagan, of course, just as the high number of moderate Dems circa 2000 is a legacy of Clinton.