Obama definitely has the home field advantage with the media in his pocket and lotsa money money money. But perhaps McCain only needs to play for a tie.

First off, we all know that polling consistently over-samples Democrats due to selection bias. This doesn’t just show up in pre-election polling, but in exit polling as well. Barack Obama has an even greater history of over-polling. This comes to us from Ace of Spades via Politico.

In theory, exit polls should match election results. But for all the care that goes into conducting accurate exit polls, errant results aren’t completely uncommon. Respected polling analyst Mark Blumenthal found that during the Democratic primaries this year, preliminary exit polls overestimated Obama’s strength in 18 of 20 states, by an average error of 7 percentage points, based on leaked early results.

The reason? Obama’s supporters were younger, better educated and often more enthusiastic than Hillary Clinton’s, meaning they were more likely to participate in exit polls.

See, Politico has finally figured out that in polling, there is this thing called “selection bias”. There is also the related variable called “get the hell out of my face and leave me alone you nosy bastards.” And exit pollsters, God love ’em, just don’t seem to be able to figure out how to quantify this.

So perhaps McCain only needs to get this thing close. The most recent Rasmussen Polls show him once again up in the must wins of Ohio and Florida. That is certainly good news.

Jim Geraghty at NRO reports on the mood of his secret mentor nickname Obi Wan Kenobi. OWK is not as worried as many of us are. He thinks the dynamic of the race changed after the last debate and that Obama is on his heels.

Obi Wan is wondering about the timing of the Colin Powell endorsement, too. I had figured that Powell’s nod would have been a bigger help to Obama earlier in the race – recall the rumors of Powell speaking at the Democratic Convention. Obi-Wan figures this was one of the best cards Obama had left to play, and he played it in the next-to-last weekend instead of the final weekend. He wonders if internal polling prompted the Obama camp to roll out Powell a bit earlier than planned.

“McCain had a very good week,” he told me. “He looked presidential at Al Smith dinner and he had everybody talking Joe the Plumber and taxes the next few days. And the debate performance may have been as big as Kennedy in ’60 — that important, because the undecideds were watching.”

“We have just seen the greatest economic scare since the Great Depression and everybody is looking at polls as if they are business as usual. That’s crazy.”

I wondered aloud whether the media’s day by day coverage could push people off those gut reactions – suspicion of “spreading the wealth around,” relating to Joe the Plumber, etc.

“If so, the American people aren’t the American people anymore,” Obi Wan responded. “Believe me, there is someone in the Obama campaign who is deathly afraid of the ‘McCain pulls even or goes ahead’ poll.” (And in Gallup, it was within 2 percent.) “That Obama strategist knows how much depends on the whole Chuck Schumer and Rahm Emanuel approach —.work with the media to demoralize conservatives, and keep the perception of a juggernaut going. But a day or two of a few bad polls, and that strategy backfires. The conservatives know they’ve still got a shot at this.”

A shot at this, that is all we can ask. Let’s get it close and maybe, just maybe we will find out that Obama has been over-polling once again. In the meantime, let’s wear out some rosary beads.