THE NATIONWIDE average gas price is up to about $3.75 per gallon of regular — time for more partisan cheap shots about energy policy. Republicans are recycling Energy Secretary Steven Chu’s remark, shortly before he took office, that the United States should “figure out how to boost the price of gasoline to the levels in Europe,” to cut consumption and help arrest climate change. Mr. Chu suggested gradually raising gasoline taxes over 15 years. Never mind that Mr. Chu has repudiated that view, or that President Obama scrawled, and underlined, the word “No” next to a gas-tax hike proposal when it came across his desk in 2009, according to the New Yorker.

And really never mind that N. Gregory Mankiw, former top economic adviser to President George W. Bush and current adviser to Republican presidential candidate Mitt Romney, also backs a stiff gas tax increase, for essentially the same reasons as Mr. Chu. In a New York Times column this year, Mr. Mankiw offered a tax overhaul that might include a gas tax “exceeding” $2 per gallon. Though Mr. Mankiw was speaking for himself, not Mr. Romney, the GOP is in no position to make that argument, given its current use of Mr. Chu’s comments against Mr. Obama.

Oh, and really really never mind the fact that both Mr. Chu and Mr. Mankiw are right: Gasoline is significantly undertaxed in the United States — in two senses. The federal 18.4 cent-per-gallon gas tax is the main source for the Federal Highway Trust Fund, but it hasn’t been raised in two decades, starving U.S. infrastructure. Also, the gas tax is set too low to offset the negative side effects for society — economists call them “externalities” — associated with gasoline consumption.

Those costs include traffic, air pollution, wear and tear on roads, climate change, and dependency on unstable sources of foreign oil. As General Motors chief executive Dan Akerson, among other industry experts, has pointed out, a permanent gas tax increase would help the U.S. auto industry, enabling it to plan for a relatively foreseeable level of fuel consumption, instead of constantly retooling its product line to suit the inefficient fuel-economy mandates Washington currently puts out in lieu of gas taxes.

The Chu-Mankiw convergence on higher gas taxes is hardly exceptional. Support for the idea spans ideology, from New York Times columnist Thomas Friedman on the left to The Post’s Charles Krauthammer on the right. Conventional wisdom isn’t always right. But in this case we should have listened to the experts and raised gas taxes higher, then indexed them to inflation, long ago.

There would have been pain at first, but, over time, increased conservation by U.S. motorists would have moderated global oil prices, causing prices at the pump to recede as well. Who knows? By now, we might actually be experiencing lower prices — and a greater portion of the per-gallon cost would wind up in U.S. coffers, instead of Saudi Arabia’s or Venezuela’s. Alas, in all the world there seems to be just one government U.S. motorists insist on stiffing: their own.