Is Mankiw One of the 'Obamicans' We've Been Hearing About
Let me offer an alternative view. Mobility makes us both more efficient and happier. Reducing the price of mobility increases our efficiency and thus our standard of living, as well as our happiness and desire to maintain and increase that standard of living. Without the artificially increased cost of mobility due to gas taxes, the true level and price of mobility would find equilibrium. Over time we would have exactly the amount of infrastructure needed to provide that amount of mobility, as opposed to now where we have infrastructure added (bridges to nowhere) or restricted (refineries) based on the political process funded by gas taxes. Mankiw seems to be arguing in favor of this sort of inefficiency. Why? Because he's bought into a scientific theory that he is not trained to evaluate properly.
I am not a fan of the McCain gas tax holiday because it is temporary and thus does not impact long term incentives, but for what it is, it represents one ever so small shift of resource allocation from the government to private citizens; and no matter how small or fleeting, that is better than were it not to happen.
UPDATE: Bryan Caplan seems to agree with me. The gas tax holiday isn't a bad idea, it's just not a terribly good one. What were people expecting, a fantastic, silver bullet of an idea that would cure our energy shortage (and that is what it is plain and simple) overnight?