I'm unsure of Bush's motives, but if the voters are thinking about terrorist threats and the security of the nation instead of the economy when they vote, he'll be happy.
My concern with a war is twofold:
1) I don't think we can take Baghdad without losing American lives and the lives of civilians in Baghdad. It's one thing to steamroll the Iraqi army in the desert; quite another to fight house to house in the streets.
2) I'm worried that it will create more enemies than it eliminates, as it would fan anti-American sentiment in many countries.
We don't have access to the information Bush et al have, though, so it's hard to know what's really going on. I wish Bush would produce more hard evidence, though.