President Obama's rating among the US public has surged following the the killing of Osama bin Laden

Two surveys released yesterday found the president's approval ratings climbed to 56%, a nine-point improvement over last month.

The polls were carried out on Monday, after details were released about the Navy Seal raid on bin Laden's fortified compound north of Islamabad, the Pakistan capital. The results were reported by The Washington Post/Pew Research Centre and USA Today/Gallup Poll.

While the killing of bin Laden has seized American and world attention, such events can prove ephemeral, particularly after a brutal presidential campaign. Mr Obama's improved approval after success in tracking down the world's most-wanted terrorist could mean little when voters enter polling booths 18 months from now.

Republicans lining up to challenge him will be banking on Americans to revert to financial issues when they cast their ballots.

With no clear front-runner yet, some of the potential Republican field will gather for a first candidates' debate of the election season in Greenville, South Carolina tomorrow. There is no doubt the field of challengers will pound Mr Obama about the nation's upward spiralling debt and what they see as a need to cut spending while rejecting tax increases.

Mr Obama remains vulnerable on the economy. The Washington Post/Pew Research Centre poll showed that only 40% of those surveyed approved of the president's handling of the economy. Other polls last week found that about 70% of Americans felt the country was on the wrong track.

The reason is obvious.

Even though the economy is slowly recovering from the Great Recession, unemployment remains near 9%, a high level for the US. Petrol prices have shot up to about four dollars (£2.42) a gallon (almost a dollar - 60p - a litre), roughly a third more than just six months ago.

As household budgets are hit hard by rising fuel costs, big oil companies raked in record profits in the first quarter of 2011. US economic growth slowed sharply in the same period, partly because of high fuel prices.

Home values continue to sink as financial institutions harvest huge earnings. The rocketing national debt is weighing heavily on the minds of taxpayers, who also fear the government will try to balance the budget by cutting away the social safety net for the poor and the elderly. The stock market and corporate profits are bounding upward, but middle-class wages are stagnant or falling when adjusted for inflation.

While Mr Obama has received generally broad bipartisan and international backing for the killing of bin Laden, Americans at the same time report increased fears about retaliatory al Qaida attacks. The USA Today/Gallup Poll survey found that more than six in 10 of those contacted said a terrorist attack was likely in the coming weeks. That, the pollsters said, was "the highest rate of public nervousness in eight years".

Nevertheless the praise for Mr Obama from unexpected quarters may portend a lingering betterment of the president's approval numbers. On the Senate floor yesterday, John McCain, a frequent critic and Mr Obama's Republican opponent in 2008, read out a statement in adulation of the military and intelligence personnel responsible for the killing of bin Laden.

"I also want to offer my deepest congratulations and appreciation to the president and his national security team," he said, referring specifically to Mr Obama's decision to forgo an aerial bombardment in favour of an airborne attack by Special Forces. "It took real courage to assume the many risks associated with putting boots on the ground, and I commend the president for it."

The polls surveyed randomly selected adults by telephone on May 2. The Post-Pew poll included 654 interviews; USA Today/Gallup interviewed 645. Both have a margin of sampling error of plus or minus five percentage points.