When Republican presidential candidate John McCain suggested suspending the federal gas tax for three months over the summer, he knew he’d tapped into an issue that might resonate with voters.

Who wouldn’t want an 18-cent per gallon drop in gas prices?

The idea seemed good to Democrat Hillary Clinton, too, as she climbed on board with the idea.

Democrat Barack Obama is the only one of the three to oppose the idea, telling people what they need to hear, not what they want to hear.

A gas tax holiday not only wouldn’t save motorists money, it would reduce highway repairs and construction, create job losses, be bad on the environment and only increase oil company profits.

Even if motorists really saw the savings, they’d be nominal — about $30 over the three months for average drivers.

But drivers wouldn’t see the savings. Removing the tax would give Americans a psychological incentive to drive a bit more. That would drive up demand for gasoline, which would increase fuel costs, wiping out or exceeding the tax savings.

Meanwhile, the tax holiday would mean the federal Highway Trust Fund would lose $8.5 billion. That’s money that would not go to states to improve highways. (The Trust Fund already has a $3.2 billion shortfall.)

An association of state transportation officials estimates that loss of highway funds would mean 280,000 construction workers would be out of work.

For environmental reasons — from global warming to air pollution — anything that prompts people to drive more is a bad idea.

Politicians can be expected to float ideas that address the biggest concerns of voters. But promoting “solutions” that would in the end harm those voters and intensify other problems is not a trait anyone likes to see in a president.

Dealing with high gas prices is complex, but politicians should be focusing on things that might really help: Pushing for fuel conservation, increasing vehicle mileage, better regulating the commodity speculators who are artificially driving up oil prices, looking at changes to the nation’s petroleum reserve and other long-term solutions.

Serious policies, not gimmicks, are needed to bring stability at the gas pumps.