WASHINGTON - The killing of Osama bin Laden, first presented as a moment of national unity by President Barack Obama, has become something else: a political weapon.

Obama's re-election campaign is portraying his risky decision to go after America's top enemy as a defining difference with his Republican presidential opponent, suggesting Mitt Romney might not have had the guts to order a mission that put lives and perhaps a presidency at stake.

Obama himself is opening up on the raid again - and opening the secretive White House Situation Room as an interview stage - to hail the one-year anniversary.

The broader goal for Obama, whether through campaign web videos or the trappings of the White House, is not to just to remind voters of an enormous victory on his watch. It is to maximize a political narrative that he has the courage to make tough calls that his opponent might not.

"Does anybody doubt that had the mission failed, it would have written the beginning of the end of the president's first term?" Vice President Joe Biden says in laying out Obama's foreign policy campaign message. "We know what President Obama did. We can't say for certain what Governor Romney would have done."

The strategy underscores the fact that the Obama who ordered the raid as commander in chief is now seeking a second term as president. The risk is the political blowback that can come if he is seen as crossing a line into politicizing national security.

"Sad," said a Romney spokeswoman. "Shameless," said 2008 Obama election foe John McCain.

Biden even combined the killing of the al-Qaida leader and Obama's support for a failing auto industry into what he called a re-election bumper sticker message.

"It's pretty simple: Osama bin Laden is dead and General Motors is alive," the vice president said in a speech on Thursday.

Obama's campaign followed that Friday with a new web video questioning whether Romney would have taken the same path Obama did. If features a quote from a 2007 Romney interview in which he said it was not worth "moving heaven and earth spending billions of dollars just trying to catch one person."

That prompted Obama's 2008 opponent, Arizona's McCain, to issue a scathing statement in which he accused Obama of playing politics with the bin Laden killing and "diminishing the memory of September 11th."

"This is the same president who said, after bin Laden was dead, that we shouldn't 'spike the ball' after the touchdown," he said. "And now Barack Obama is not only trying to score political points by invoking Osama bin Laden, he is doing a shameless end-zone dance to help himself get re-elected."

The president's initial words on the bin Laden mission - a raid for which he received wide praise, including from Romney - were ones of sober thanks. Addressing the nation late that night of May 1, 2011, in Washington, Obama said: "Tonight, let us think back to the sense of unity that prevailed on 9/11."