This Christmas, you'll believe that a lame duck can fly.

Seriously, movie-trailer lingo aside, what's up with this new storyline down in Washington? A flurry of major legislation - capped by three major, long-gridlocked measures passed since Saturday - has made it impossible for any pol to pull a Harry Truman and rail against the "do-nothing Congress," at least not for a while.

Just yesterday, President Obama signed into law the measure allowing gays to serve openly in the military - hours before winning final Senate approval of his administration's New START arms-control treaty with Russia and seeing a deal for billions in aid to ailing 9/11 responders.

"We are not doomed to endless gridlock," a suddenly upbeat Obama said yesterday, as some pundits hailed this so-called "lame duck" session - the final days of the 111th Congress before a more heavily Republican one takes office Jan. 5 - as the most productive since World War II.

But even many talking heads are stunned after wrongly predicting that GOP senators who've blocked much of Obama's agenda the last 22 months would continue until the 112th Congress convenes.

Q. So what changed?

A. Call it the only thing that could make things move inside the Beltway - a political perfect storm.

Everyone knew that Obama and congressional Democrats had a powerful motivation to get things done now, before the House flips into GOP hands and Republicans strengthen their ability to filibuster in the Senate.

But political experts like Larry Sabato, the University of Virginia history professor and pundit, say people didn't realize some moderate Republicans were also motivated to act before the conservative tea-party movement gains more steam.

"The tea party doesn't understand that you still need the president's signature," said Sabato, who said some Republicans feared that the party's right wing would have pushed in 2011 for harsh spending and tax cuts that Obama would not agree to. What's more, the so-called Bush tax cuts would have expired on New Year's Day without a deal, and neither party wanted to risk voter wrath about that.

Q. But what do tax cuts have to do with gays in the military or U.S.-Russian relations?

A. In theory, nothing. In reality, last week's vote to extend the tax cuts (even for the wealthiest 2 percent of Americans whom Democrats wanted to drop from the measure), and to provide emergency unemployment benefits and cut payroll taxes for one year, cleared the logjam to allow votes on these other issues.

And unlike tax-and-spending issues where the GOP is remarkably unified, some Republicans are inclined to side with Obama on social issues or foreign policy.

Q. So what actually happened this week?

A. A lot - ready?

* "Don't ask, don't tell": Obama finally kept a 2008 campaign promise to overturn a Clinton-era policy in which uncloseted gays could be kicked out of the armed forces. The president said he hopes the military can implement a new policy in a matter of months that will allow gays to serve openly.

In the end, only 31 socially conservative senators, mostly Republican, opposed the measure, while blue-state GOPers like Sen. Scott Brown, of Massachusetts, supported the move - also backed by most Americans, according to polls.

* New START treaty: Unlike regular legislation, treaties go only to the Senate for ratification, where a two-thirds vote is required. Support for the pact with Russia from every living former Secretary of State - including five Republicans - convinced veteran GOP senators like Richard Lugar, of Indiana, to hop on the bandwagon.

* 9/11 responders: Even Washington insiders seemed flabbergasted initially by GOP opposition to a measure to provide federal funding - scaled back to about $4.3 billion in the final bill - for health problems suffered by police, firefighters, and others exposed to toxic chemicals in responding to the 9/11 attacks.

Ironically, reflecting the bizarre political zeitgeist of 2010, the turning point for the once-stalled measure may have been a campaign for its passage by a comedian, Jon Stewart, of Comedy Central's "The Daily Show."

* Food safety and child nutrition: Even measures like these that used to be legislative slam dunks seemed lost at one point to partisan gridlock, but Obama signed the child-nutrition bill on Monday and the food-safety measure is back on track.

Q. Gosh, is there anything Congress didn't do?

A. Yes. One notable measure that failed to win passage was the so-called DREAM Act that created a path to citizenship for undocumented youth who serve in the military or earned a college degree in America. Anti-illegal immigration forces successfully lobbied the GOP - even Arizona Sen. John McCain voted against an idea he once sponsored - and conservative Democrats to kill the bill.

The 111th Congress also punted on spending issues, postponing a major fight on funding the federal government until early 2011. Indeed, lost in the euphoria was the fact that while the logjam broke for popular items like tax cuts, it didn't for politically hard votes on slashing programs.

Q. Are the pundits going a bit overboard in suddenly calling Obama "The Comeback Kid" and hailing the session as a huge victory for him?

A. Perhaps. Some of the same folks declared the Obama presidency dead in the water a month ago. But several polls seem to confirm a boost for the White House, perhaps because Obama was seen as triumphing over initial GOP obstructionism on issues with majority public support, such as the 9/11 responders' aid.

A CNN/Opinion Research Group poll released yesterday found that 56 percent of Americans approved of the way that Obama handled the lame-duck session, while only 42 percent approved of its handling by congressional Republicans.