The presidential election is far from decided with 43% of registered voters saying they haven't made a final decision on who they'll vote for president. An AP poll found that most of the undecideds, according to a New York Times story, tend to be "gloomier than others about the country, with fewer than one in eight saying the U.S. is heading in the right direction. They also are likelier to be white and male and to consider themselves moderates and independents than those firmly committed to candidates."
I think the uncertainty in the economy and the world would tend to cut in McCain's favor because of his experience. I think people will what to go with a known commodity rather than the unknown. Normally, a poor economy would favor Obama who represents the party out of power. If Obama remains the issue, that's a problem for him.
The race will likely go down to the wire. We maybe returning to the days of divided government, like much of the 70s and 80s where Democrats control the Congress and Republicans the White House. I don't know that people make a conscious decision in this regard but maybe that's how things will end up after November.