FAIRFAX, VA. - Both Sen. Hillary Clinton (D.-N.Y.) and Sen. John McCain (R.-Ariz.) say that we should suspend the 18-cent-per-gallon federal gas tax this summer. After Clinton's beating at the polls Tuesday, there may not be much reason left to worry about what Clinton thinks, but the McCain proposal is alive and well.

Most economists oppose the Clinton-McCain "gas-tax holiday" because they can't see how consumers will benefit. In fact, "most" is an understatement: When challenged to name one economist willing to back her plan, Clinton's response was to disparage the whole profession.

Why are economists so opposed? In the short run the supply of gasoline is basically fixed, because it takes awhile to build a new refinery. The demand for gasoline, in contrast, is more responsive to price. We're already seeing greater use of public transportation and brisk sales of fuel-efficient cars. When you combine fixed supply with flexible demand, it is suppliers, not demanders, who will pocket the tax cut. That's Econ 101.

So far I pretty much agree with the consensus. Economists may overstate the rigidity of supply -- it's possible that eliminating the tax could spur producers to find a way to squeeze out a little more gas -- but they're probably right that the Clinton-McCain proposal will not shrink the price at the pump.

Nevertheless, I think it's an idea worth supporting. In fact, I've got two arguments in favor of it, though I doubt that either candidate will want to repeat them in public.

The first is that the tax holiday is a relatively cheap symbolic gesture that makes truly bad policies less likely.

The main causes of high gas prices are probably factors beyond our control, such as rapid growth in China and India and low real interest rates. But voters don't want to hear this. They want politicians to "do something!"

During our last big energy crisis, in the 1970s, "something" turned out to be a salad of populist nonsense: price controls, rationing, windfall-profits taxes, arcane loopholes and lots of lawsuits. That political response turned an inconvenience into a disaster.

We can do better this time. Since in an election year Congress will feel compelled to show the voters that it feels their pain, let's do something that at least keeps energy markets in good working order. The tax holiday fits the bill. Markets will adjust to it, no problem. And it won't cost much -- the estimated $9 billion in lost revenue is about $30 per person. That's not a bad price to pay for a little insurance against a rerun of misguided 1970s measures.

Second, even a "giveaway to the oil industry" sets a positive course for the future. During the last crisis, the industry was a scapegoat for scarcity. Politicians scrambled to stop oil companies from profiting from the crisis, even though temporarily high profits end shortages by giving businesses an incentive to figure out how to increase output.

It's naive to think that the oil companies have forgotten the 1970s. They know that there's a decent chance that economic populism will return. In fact, it already has: Clinton's full proposal is to combine her tax holiday with a 1970s-style windfall-profits tax.

In this light, that oil companies might pocket most of the tax cut could easily be a good thing. It helps cancel out the negative legacy of the last energy crisis -- public hysteria occasionally will work in your favor. This makes the energy companies less likely to hunker down on their profits and more likely to do what they didn't do enough of in the 1970s: search for ways to increase production.

In a perfect world, policymakers would respond to energy crises with benign neglect. In the real world, though, they know that constituents want action. So it's better for them to balance their abuse of the oil industry with an occasional olive branch. In that sense Clinton's pairing of an excess-profits tax with a gas-tax holiday isn't nearly as bad as an excess-profits tax all by itself.

This sounds cynical, but I'm simply being honest. Politicians are constrained by public opinion. When the public rejects the mundane explanations for high gas prices -- big, boring facts like rapid Asian growth -- politicians aren't going to correct them. The best we can expect is for Washington to try to channel the public's misconceptions in relatively harmless directions.

We could do much worse than the gas-tax holiday. In fact, we usually do.

(Bryan Caplan, author of "The Myth of the Rational Voter: Why Democracies Choose Bad Policies," is an associate professor of economics at George Mason University.)