After a lackadaisical six months, Congress roared to life in the lame-duck session, passing a sweeping tax package, a stop-gap funding bill, a food-safety law, and improbably repealing the military's "don't ask, don't tell" policy on gay service members. The Senate is also likely to ratify President Obama's New START nuclear treaty with Russia. That list of accomplishments is all the more impressive because in lame-duck Congresses, "traditionally nothing meaningful is done," says NPR's Corey Dade. Here are six explanations for this burst of activity:

1. Deadlines focus the mind
"Congress seems to work better under deadline pressure (like journalists)," says Tabassum Zakaria in Reuters. And for the Democrats, the big deadline is the start of the 112th Congress, when Republicans gain a lot of power. This push "proved that Congress still can do things — big things — when they so choose," says Chris Cillizza in The Washington Post, even if "much of the agenda of the lame duck was put there because lawmakers didn't want to tackle the dicey issues pre-election."

2. Congress isn't really "broken" after all
Assuming New START passes, my "faith in the legislative process might — just might — be restored," says Chris Good in The Atlantic. That would be especially remarkable coming "just a month and a half removed from the rank partisanship of the November 2010 midterms, which left serious doubts over Washington's ability to agree on anything." Apparently the "guiding post-election wisdom" about looming gridlock just wasn't that wise. This Congress looked "appalling, depressing, spirit-deadening, and completely sub-optimal," says Martin Longman in Booman Tribune. But "go figure" — people will remember it "as the best and most consequential of most of our lifetimes."

3. Even after the elections, the Republicans caved
The Democrats are using their last hurrah to push through legislation that they were too timid to tackle before Election Day, says Kurt Hyde in The New American. And "for some unexplained reason," the GOP is letting them. The Republicans in the Senate could have forced an end to the lame-duck session, but instead they've let the 111th Congress "do more damage to the American Republic" during this session "than it did during the first 22 months of its ignominious existence." It's part of a bad trend, says Chris Stirewalt in Fox News. "As they have become more common, lame-duck sessions have become more ambitious and lawmakers less abashed about legislating without a mandate."

4. The bills tackled weren't really that politically tough
The productivity of this lame-duck Congress "has been a surprise," but many of the bills it passed shouldn't have been this difficult to push through, says USA Today in an editorial. Repealing DADT was "momentous," but it will appear "inevitable" with a few years' hindsight. Ratifying the nuclear treaty "should have been one of the easiest" things to get done this year. The tax deal was less a compromise than giving Republicans cake and Democrats ice cream. And Congress failed when it came to one of the "few jobs it absolutely must do every year": Passing an annual appropriations bill to fund the federal government.

5. The election scared up a few moderate Republicans
Pop quiz: Which one Republican sided with Obama on DADT repeal, the DREAM Act, the tax deal, and New START? asks Steve Benen in Washington Monthly. Sen. Lisa Murkowski of Alaska, whose party "actively tried to defeat her" after she lost the GOP primary to Tea Partier Joe Miller. GOP leadership can't like that Murkowski is siding with Obama more often than some Senate Democrats, but she "not only doesn't care, she actually has an incentive to annoy them." With every vote so crucial, her's really counted.

6. Presidential leadership
Obama's "string of major legislative victories" in the lame-duck session started with his big tax cut deal with Republicans, says NPR's Corey Dade, and built from there. Getting Congress to "enact several of his top priorities" was no mean feat for a president who "emerged politically wounded" from his midterm "shellacking," says Peter Baker in The New York Times. And while Obama had to "swallow a compromise" in the tax cut package, and played a supporting role in repealing DADT, his "unusually relentless campaign" for New START made it a "high-profile test of his clout." His new "willingness to be the salesman-in-chief" had a big impact on the session, says The Washington Post's Chris Cillizza, and helped his political standing, as well.