WASHINGTON - US President Barack Obama's use of big stick power to eliminate Osama bin Laden may deprive Republicans of one of their most trusty political tactics: branding Democrats as national security weaklings.

The risky raid deep into Pakistan that killed the al-Qaida chief nearly 10 years after the Sept 11 attacks came at a time when Obama was on the backfoot on foreign policy and as he fired up his 2012 bid for a second term.

There was no suggestion the operation was a fiendish plot to improve his poll numbers, but politics are shaped by events. Public perceptions of a leader's mettle on the world stage are an important driver of presidential elections.

Republicans have often criticized Obama for being hesitant to wield US might, but by acting with decisive force against the United States' most reviled foe, he has enhanced his stature, at home and abroad.

Conservatives have also rebuked Obama for "apology tours" abroad, accused him of embracing US enemies at the expense of allies and, until Sunday's raid, lambasted him for "passivity" over revolts in the Arab world.

After Obama gambled on a secretive, risky special forces mission to at last avenge the attacks that killed nearly 3,000 people in the United States, that case became harder to make.

"Their talking points have to change ... the narrative that we are not strong in the war on terror - that cannot be done now," said Steve Clemons of the New America Foundation.

"His credibility as a hard power guy just went up a few notches.

"It makes him a much less vulnerable target," added Clemons, publisher of the influential blog The Washington Note.

The president won praise from an unlikely source on Wednesday, The Wall Street Journal's reliably conservative editorial page.

Foreign policy writer Bret Stephens predicted the episode would squelch conservative conspiracy theories about Obama's birthplace, which the president was forced to address last week after they erupted into mainstream politics.

"If there ever was a doubt about how American Mr Obama is, Sunday's raid eliminates it better than any long-form birth certificate," said Stephens.

"This was his finest hour."

While the political world awaits data assessing an expected "bounce" in Obama's diminished poll ratings in the wake of bin Laden's demise, it is doubtful the president can ride the wave all the way to next year's election.

Events always upset best-laid campaign plans, and bin Laden's death, while a huge symbolic success for Washington, may not improve US vulnerability to terror groups or ease a thicket of foreign policy challenges.

And a major future stumble by the president on a national security crisis could still change the picture before the next election.

"Right now, he is in good shape on this question - but I would add the caveat that this is always subject to events," said Bruce Buchanan, a political scientist at the University of Texas at Austin.

US elections are traditionally fought on economic territory, and Republicans may hope that rising gas prices, high jobless figures and stunted economic growth will dash Obama's hopes of a second term.

Foreign policy triumphs are also no guarantee of success at the polls: George H.W. Bush won the Gulf War in 1991, but was turfed out of office in an economic downturn by Bill Clinton in 1992.

As Obama embarks upon his re-election run, Republicans have been dusting off familiar themes, consistent with an effective decades-long narrative according to which Democrats lack fire in the belly.

His decision to allow European nations to take the lead in protecting civilians after an initial US blitz in Libya exposed the president to charges he was confused and reticent in projecting US power abroad.

"We used to relish leading the free world, now it's like leading the free world is an inconvenience," Republican Senator Lindsey Graham told Fox News.

Graham's theme was a familiar one. In 2004, then-president George W. Bush regularly slammed his Democratic presidential opponent John Kerry as soft on terror - using the Sept 11 attacks as a prism.

Agence France-Presse