Greg Mankiw explains why the issue of the gas tax proposed by McCain and Billary matters:

This issue is like the canary in the coal mine: No one really cares about the canary, but its condition tells us about deeper problems that lie below.

Many economic issues (e.g., health care, corporate taxation, the trade deficit) are vastly complicated, with experts holding a variety of opinions. When candidates disagree, it simply means that each is siding with a different set of experts, and it is hard for laymen to figure out which set of experts is right. By contrast, the gas tax holiday is not nearly as complicated, and the experts speak with one voice.

Why, then, are candidates proposing the holiday? I can think of three hypotheses:

Ignorance: They don’t know that the consensus of experts is opposed.

Hubris: They know the experts are opposed, but they think they know better.

Mendacity with a dash of condescension: They know the experts are opposed, and they secretly agree, but they think they can win some votes by pulling the wool over the eyes of an ill-informed electorate.

So which of these three hypotheses is right? I don’t know, but whichever it is, it says a lot about the character of the candidates.

With this test in mind, Obama comes out ahead.