The L-word is quietly working its way back into the political lexicon.

The number of voters identifying themselves as "liberal" jumped three points on Election Day, from 22 percent in 2008 to 25 percent this year. That's the highest that number has been since at least 1976, according to exit polls.

The term "liberal" has long been somewhat of a pejorative in American politics -- or at least been less popular than the alternative.

When Ronald Reagan was reelected in 1984, just 17 percent of Americans identified as "liberal." And even back when the founder of the New Deal, Franklin Delano Roosevelt, took 61 percent of the vote in 1936, it was more popular to be a "conservative" than a "liberal," as Wonkblog's Ezra Klein pointed out.

That may be changing, though. While the "conservative" label has stayed about where it is, self-described liberals have increased from 17 percent of the electorate in 1980 to 21 percent in 1992 and now 25 percent today.

And the three-point jump between 2008 and 2012 is tied for the biggest jump in the last three-plus decades.

Here's how that looks on a graph:

Now, this shouldn't be over-sold. We've still got far fewer people identifying as "liberals" than identify as "conservatives" (35 percent). And we have yet to see a stampede of Democrats rushing to embrace the label.

But for a label that Democrats have shunned for a while now, it seems to be on the ascent.

So what gives? A few theories:

* Obama: Undoubtedly, President Obama's efforts to enunciate a more active role for government played a role. In the 2012 campaign, Obama talked about government in a way that many Democrats haven't in recent years. And while he may not call himself a liberal, his policies are generally regarded as such. Thus, Obama supporters are less reticent to embrace that label. In 2004, 39 percent of Democrats IDed as "liberals"; that number is now up to 46 percent.

* The Bandwagon Effect: The Democratic Party is riding high. Democrats just won a majority of the popular vote in consecutive presidential elections for the first time since -- you guessed it -- FDR. And as we've said, they've done it with a president who is regarded as a liberal. For some, we're guessing, Obama's wins serve to reinforce the idea that it's okay to be liberal.

* Polarization: The country is increasingly polarized, and the Democratic Party is more liberal. While Democrats used to have a healthy share of moderate and conservative Democrats in the South and in rural America, most of those members have been kicked out of office, replaced with more liberal (though in some cases still moderate) Democrats from the suburbs. As we've written before, House Minority Leader Nancy Pelosi (D-Calif.) is surrounded by a significantly more liberal caucus than she was when she was speaker, and she herself, of course, is one of the most liberal members of the House. And in the Senate, it seems the new Democratic caucus will be more liberal than its predecessor.

* Demographics: Some of the fastest-growing demographics in the country happen to the ones that are trending toward the "liberal" label, including non-religious people (rising from 18 percent liberal in 2004 to 24 percent today), college graduates (from 48 percent to 53 percent) and Hispanics (from 10 percent to 13 percent). Young people, of course, have always been pretty liberal; the label's increasing appeal to these groups means it is gaining steam.

* The social issue shift: The country continues to tilt to the left when it comes to social policy. In 2012, multiple states for the first time voted to legalize recreational marijuana and gay marriage, and a swing state -- Wisconsin -- even elected a liberal Madison congresswoman who will become the first openly gay senator, Tammy Baldwin. It's been a marked shift from the days of George W. Bush, when Republicans won by emphasizing their conservative positions on social issues.

Peyton M. Craighill and Scott Clement contributed to this report.