Barack Obama has beaten John McCain in the vast majority of polls since Obama became the Democratic nominee for president. Even before that, both Hillary Clinton and Obama were beating McCain; the big bone of contentions between supporters of the two Dems was by how much they were beating McCain.
So the storyline should go something like this: Even though he's been running for president for an amazing 10 years straight, McCain is already behind Obama, who voters are still getting to know. Voters aren't going to suddenly discover something new to like about McCain, so McCain knows his only shot is to bring Obama down to his level by driving up Obama's negatives. Especially with his literal embrace of President Bush, McCain is practically the incumbent here. McCain is behind and not built for a comeback.
But the media's storyline instead has been "Why isn't Obama winning by more?" It's as if Obama's consistent lead over McCain for most of the last year doesn't even exist. In fact, some coverage goes so far as to imply Obama is losing. As TPM points out, the New York Times' Katharine Seelye today inexplicably claims, "Mr. Obama is struggling in the polls to maintain parity with Senator John McCain."
Is the media creating a point spread for Obama? In effect, saying Obama has to be up on McCain by a certain margin or he will be, in the eyes of the media, losing? Is it part of the media more broadly grading McCain on a curve on his repeated mistakes and gilded background?
There is also the entertainment component: presenting the "narrative" as a tight horse race with breathless examination of one candidate's every utterance and every move, based on the latest talking points and framing done by the other candidate's handlers, keeps the lumpken voter glued to the broadcast, and makes the job of the so-called reporter easier, who no longer exerts himself to do any investigative reporting; he just report the stats as he fantasizes them, including home runs, RBIs, errors, just like a baseball game. Sure saves effort.