I was watching cable news during part of the run-up to the House vote on health care reform (because I was at the gym, which is where I tend to watch cable news). And the most shocking but entirely unsurprising thing happened. Wolf Blitzer was suddenly pushing back on Republican talking points, which had seemed so reasonable to him for the last year and a half. In fact, when Democratic guests wouldn't push hard enough against the conservative talking points, the Blitzinator would call the Republican out himself.

Suddenly Wolf had realized that this bill was actually an extremely moderate and centrist plan! Anyone calling it communist totalitarian socialism needed to explain himself, prontissimo!

Meanwhile, over at 60 Minutes, where Katie Couric was interviewing Rahm Emanuel, health care reform was still poisonously unpopular political Kryptonite. Why would you do that to yourself, Rahm? Do you lack basic survival instincts? Have you asked your physician about Zoloft?

The difference between these two media narratives? Blitzer was live and Couric was pre-taped. Blitzer knew the Dems would win, so his story was all about what great strategists they were and how out of step the Republicans were from the American mainstream. Couric was still in the previous media narrative, in which the Democrats were doomed to lose and therefore out of step from the American mainstream.

It's that simple. There's not much else to it.

The mainstream media is driven by two basic factors: who's winning (which, between national elections and major legislative votes, means who is perceived to win), and how old the existing narrative is. Democrats don't have the votes lined up? America is on the dawn of a New Conservative Era. Democrats win the vote? The Democratic leaders are political geniuses, whose management secrets we all need to learn. These examples should be jokes, but are not. Blitzer has essentially said both things.

Obama's portrayal in the media is about to change from ineffectual over-intellectual Jimmy Carter II, which is who he was alleged to be two weeks ago, to electrical and oh-so-sexual Lincoln Delano Kennedy, which is who he's alleged to be when he's won something. That is stupid, but at least partially fair. A President who manages to enact his policy should get credit for enacting it. (Whether or not the policies are good is another, more important but widely ignored question.) The truth is, Obama periodically gets hyped in ways no politician could live up to, but is a pretty smart and effective president. He's not Jimmy Carter II by any means.

The other problem is that the media has amnesia, and gets bored with a story after they've run with it for a while. The Jimmy Carter II story was inevitable, simply because the media got tired of running Obama the Conqueror stories, and because after a while Obama hadn't won any elections for six! whole! weeks! The Jimmy Carter II story was also never going to last, because the media would get bored with that, too. (The idea that unpopular Obama was going to drag down the ticket in November was always silly, because the "unpopular Obama" story was never going to last for a full six months.)

Obama will be "up" for a while, and then he will be "down" again, and then the media say he's "up" again. Part of that will be tied to external events, but those events are merely convenient hooks for a inevitable rhythm of media coverage. Obama will "ride high," Obama will "struggle." Our political media can't accept the idea that something stays true for four years in a row ... and anyway, that would be boring.