President Obama's political fortunes have taken a sharp turn upward since his party's November "shellacking" in the midterms, according to several recent polls. CNN shows Obama with a 55 percent approval rating, NBC News/Wall Street Journal has him at 53 percent, and Gallup notched Obama at 50 percent for the first time since May. What's behind this resurgence in Obama's popularity? Here, five theories:

1. Health care isn't toxic anymore
There are lots of reasons for the surge in Obama's poll numbers, but a big factor "is that support for repealing his signature legislative accomplishment, the health care overhaul, is finally ebbing," says Jon Terbush in Talking Points Memo. As Republicans double down on repealing "ObamaCare," polls this year show a plurality of voters either want to keep the law intact or even expand it, while only about one in five wants Congress to scrap it.

2. The voters got "catharsis"
The analogy is a little "cheesy," says Mickey Kaus in Newsweek, but let's say Obama is like a "profligate spending" spouse, and the voters are the wife who blew up at him and cut up his credit cards in November. Then, after the blowup, they felt better about Obama "almost immediately," as the polls show, "without him having to do anything." Call it the "catharsis theory" — "Catharsis + Absence of Offense + Time = Popularity" — and it suggests Obama will stay up in the polls as long as he doesn't lapse back into "old-style liberal politics."

3. The public likes him taking care of business
The big uptick in Obama's poll numbers came after the lame-duck session of Congress, which "tackled many of Obama's agenda items," says Ben Terris in National Journal, including a repeal of "don't ask, don't tell" and a new nukes treaty with Russia. "By showing his legislative clout in the lame duck," Obama has revived his fortunes, and "the clear implication is that Americans want the government to get things done, not to be mired in gridlock."

4. Voters are feeling more optimistic
It's no coincidence that Obama's jump in the polls tracks a "surge in optimism about the state of the nation" and the economy, says Paul Steinhauser at CNN. A majority of Americans (56 percent) still say they don't feel things are going well in the country, but even before Obama's "sunny" State of the Union address, the pessimism numbers were way down. "We haven't seen numbers this good since April of 2007," says CNN polling director Keating Holland. Of course, voters tend to express more optimism at the beginning of any year. (Watch a CBS News report about Obama's rising poll numbers)

5. The White House has found its voice again
Last year, the Obama team failed to offer a consistent, positive narrative and got bogged down in tactical legislative battles, says outgoing Obama political guru David Axelrod, in Bloomberg. "We got so enmeshed in the details of governing that we stopped telling the story," he says, but "we did that better in the last 60 days." As the polls show, "we've righted the ship."