People seem to be focusing on the total head-to-head numbers in the Presidential election tracking polls, which currently show Senator Obama with a nine point lead. These charts indicate why those numbers are solid.
The last figure is the most important. For the last year, the Republicans have been trying to paint Senator Obama as, at best, an elitist, and at worst, a terrorist sympathizer and closet Muslim. Yet, more Americans indicate that Obama shares their values. Even though the lead is narrow in the last chart, judging by the other numbers, it's solid.
Given this, I believe that, barring a political earthquake, Senator McCain cannot win. Political races tend to tighten in the final weeks, but I still believe that Obama/Biden will enjoy at least a 4% popular majority and end up with at least 330 Electoral votes.