Deeply embarrassing, but not entirely the campaign’s fault. If memory serves, Romney’s Big Bird line was the thin reed to which liberals on Twitter were clinging the morning after the Denver debacle:

“There’s been a strong grassroots outcry over the attacks on Big Bird. This is something that mothers across the country are alarmed about, and you know, we’re tapping into that,” Psaki told reporters aboard Air Force One on Wednesday…

“The larger point… is, aside from our love for Big Bird and Elmo, as is evidenced by the last few days, the point that we’re making here is that when Mitt Romney… was given the opportunity to lay out how he would address the deficit, when he said ‘I will take a serious approach to it,’ his first offering was to cut funding for Big Bird,” Psaki said. “And that is absurd and hard to take seriously his specific plan.”

Two problems. First, needless to say, Romney’s point about PBS isn’t that serious deficit reduction should start there, it’s that not even popular federal outlays should be immune from cuts in the name of restoring fiscal stability. A guy who bet his presidential candidacy on Paul Ryan is about as serious as an American politician can get when it comes to spending. And let me gently suggest to Team O that any campaign that treats the Buffett Rule as an important budgetary reform shouldn’t wag its finger too sternly in criticizing others for half-measures. Second, the Big Bird ad is actually very typical of Hopenchange’s M.O. this year. They’ve tried to bludgeon Romney with every cheap demagogic populist ploy within reach. How were they supposed to lay off an easy opportunity to suggest that Mitt hates moms and kids and puppets? What’s unusual about the spot isn’t that it’s trivial, it’s that they released it at a moment of real momentum for Romney, which in turn makes them look desperate and inept. Per Sean Trende’s superb analysis today at RCP, it’s very important to Obama’s campaign that they be seen as winning at all times. A winner can get away with a silly ad like this; a guy who just got his ass handed to him in front of 70 million people really can’t. Trende:

I’ve superimposed the major events of the 2012 cycle here. The basic trend line is fairly plain. Over time, the president’s lead gradually deteriorates. When it gets too close, he makes a major play to change the dynamic, pushing the lead back up…

I do think there is a degree to which Team Obama has successfully (and quite frankly brilliantly) created a “virtuous cycle” this election. There are three ways in which this is the case.

First, the bandwagon effect affects fundraising. Once you move outside the partisan core, people like to back winners. This is especially true of the business community. By assiduously cultivating its front-runner status, the Obama campaign has aided its ability to press future arguments.

Second, maintaining a lead allows greater leeway in the arguments it can make. Something like the “cancer ad” from August looks hard-hitting from a campaign that is leading (and I certainly include candidate super PACs as part of the “campaign”), but would probably be described as “desperate” from one that is losing.

Finally, and perhaps most importantly, it affects press portrayals of the candidates and party enthusiasm. This is the most important thing here: I still think the default expectation here has been that Obama should be losing.

In other words, every time the basics of the economy and the deficit and some new foreign-policy debacle start to eat into Obama’s lead, he latches on to a new shiny object that can boost his lead by a few points — until the basics (“gravity,” in Trende’s phrasing) start to drag him down again. The more consistently he’s seen as a winner, the more Romney smells like a loser, which has all of the self-fulfilling effects that Trende describes above. The reason the debate was such a killer was that it shattered that perception of Obama’s invincibility that he’d spent the last nine months cultivating. And the last thing you want to do once that’s happened is make yourself seem ridiculous by running a silly ad that’s transparently an attempt to change the subject — especially if you got elected the first time by scolding people for the “smallness” of their politics. Watch the two clips below, the first via the Examiner and the second via the Right Scoop, and see for yourself who looks small now. Just look at what this guy’s “new kind of politics” nonsense has become. Click the image to watch.