When Bill Clinton fought the 1992 presidential campaign against George H. W. Bush he had a sign hung at his Little Rock Headquarters with three key messages written on it as reminders for the campaign.
1. Change vs more of the same.
2. The economy stupid.
3. Don't forget health care.
Obama clearly has learned the lessons from that campaign and it's hard not to see this as something like a re-run.
Then as now there was recession although the US was coming out rather going in. Bush Snr had also presided over a short and decisive Gulf War in comparison to the poorly executed occupation that Iraq turned into.
With the economic crisis that has engulfed the world yet to be fully resolved attention in the present campaign has turned yet again to the economy and the Obama camp would be shouting that "it's the economy again stupid." except that they probably don't want to be seen too obviously aping the Clinton campaign.
Reading the runes of this particular US election doesn't look hard at the moment. Obama looks to have the momentum and the course of events on his side. If US citizens are in the mood for change then Obama clearly embodies this more than McCain. The polls recently seem to show that people trust Obama more on the economy than McCain. In the middle of a financial crisis that must be the match winner.
Nothing is certain in politics but barring a fall at the final hurdle it's hard to see McCain catching Obama as he races for the Whitehouse crying "It's the economy again stupid !"