From the comments:
This is Econ 101. With a near-vertical supply curve--which is the case during the summer--a tax cut has no effect on the market price. The only consequence is an increase in the producer surplus. I drew up the relevant supply and demand graph on a post at our [Economists for Obama] site.
My reply:
Thanks for the comment, I've made this a separate post. And what do you think about the Obama's notion that lower prices will increase demand?
Note to everyone: This isn't about politics for me ... all 3 candidates are butchering economics right now but today's favorite butcher is Obama.