If we attack Iran and oil prices skyrocket to 200 a barrel, there could well be a 1980-type wave against the Republicans. People need gas to get to work.
I think that if US attacks, or if Israel does (which would lead to a US participation, yes, if Israel attacks, Iran retaliates, and so US attacks Iran to defend Israel...), 200$ the barrel could be the price when the news would say that the first rocket is fell on the Iranian ground. Then, it could go higher and higher, imagine everything what can happen just in the Persian Gulf if such an attack is launched.
Then, do you really think that peoples will think that choosing Democrats in such circumstances will give them a less expensive gas? Or do you think they could choose Dems to punish the Reps to have gone in a such war? Personally, I would be surprised of both.
To me an Iranian war under Bush administration, what we are talking about, would lead more peoples to the experience of Mc Cain than to the youth of Obama.