Soaring gasoline prices are threatening to undercut President Barack Obama’s re-election prospects and offering Republicans an easy target. With prices pushing $4 a gallon and threatening to go even higher, Obama sought Thursday to confront rising public anxiety and strike back at his GOP critics.

“Only in politics do people root for bad news, do they greet bad news so enthusiastically,” Obama said of Republicans. “You pay more; they’re licking their chops.”

Obama said dismissively that all the Republicans can talk about is more drilling — “a bumper sticker … a strategy to get politicians through an election” — when the nation’s energy challenges demand much more. In a speech in Miami, he promoted the expansion of domestic oil and gas exploration but also the development of new forms of energy.

For all the political claims, economists say there’s not much a president of either party can do about gasoline prices. Certainly not in the short term. But it’s clear that people are concerned — a new Associated Press-GfK poll says seven in 10 find the issue deeply important — so it’s sure to be a political issue through the summer.

“Right now, we’re experiencing yet another painful reminder of why developing new energy is so critical to our future,” the president said. At an average of $3.58 a gallon, prices are already up 25 cents since Jan. 1, and experts say they could reach a record $4.25 a gallon by Memorial Day.

Those higher prices could hurt consumer spending and unravel some of the recent improvements in the economy. And they could also be a daily reminder to voters to question Obama’s contention that he’s making the nation — and them — more secure.

While motorists are already starting to complain, many economists see the $4-a-gallon mark as a breaking point above which the economy starts to suffer real pain. Analysts estimate that every one-cent increase is roughly a $1.4 billion drain on the economy.

Obama’s Republican challengers aren’t letting it all slide by. They have stepped up their attacks on his energy policies, including his rejection last month of a pipeline to carry oil from Canada to refineries on the U.S. Gulf Coast. And they’re full of promises.

“I’ve developed a program for American energy so no future president will ever bow to a Saudi king again, and so every American can look forward to $2.50-a-gallon gasoline,” former House Speaker Newt Gingrich said in the Wednesday night GOP debate in Mesa, Ariz. He calls his strategy “Drill Here, Drill Now.”

At the same event, former Sen. Rick Santorum of Pennsylvania — who has warned of $5-a-gallon gas — asserted that “we have a lot of troubles around the world, as you see the Middle East in flames and what’s going on in this country with gas prices and the economy.”