Barack Obama has launched a withering attack on his presidential rival Mitt Romney for trying to turn the wave of attacks on US embassies around the Arab world into a political opportunity.
Normally America's politicians declare a truce on attacking each other at times of national crisis.
But the death of US diplomats, including its ambassador to Libya Chris Stevens on the anniversary of 9/11, has instead provoked a row at the very heart of the race for the White House.
Mr Romney received criticism even from Republicans for the timing of his remarks about the Obama administration's handling of the crisis in the Middle East.
With the election just eight weeks away, some believe Mr Romney has done himself serious damage.
Even as the attacks were unfolding, Mr Romney accused the president of weakness in his response, saying a statement from the US Embassy in Cairo was "akin to an apology" for American values.
That statement, which affirmed an American policy of religious tolerance and respect, was released before protesters had breached embassy walls and had not been cleared by the White House or State Department.
Twelve hours later Mr Romney defended his decision to criticise Mr Obama. Asked if he would have done so had he known about the deaths, he said: "I'm not going to take hypotheticals about what would have been known and so forth."
Mr Romney had chosen to speak before the president addressed the nation and ended up facing a barrage of questions from reporters in an impromptu news conference.
Mr Obama was critical of his rival in an interview with CBS News '60 Minutes'. He said it showed "Romney has a tendency to shoot first and aim later".
He added: "It appears that Gov. Romney didn't have his facts right."
As president, he said: "It's important for you to make sure that the statements you make are backed up by the facts, and that you've thought through the ramifications before you make them."
Even senior Republicans have failed to support Mr Romney's remarks. Representative Peter King, Republican chairman of the House Homeland Security Committee, said Mr Romney's remarks "could be perceived as being political".
He added: "I probably would have waited 12 or 24 hours and put out a more comprehensive statement."
Conservative commentator Peggy Noonan, a former Republican official, said Mr Romney was not "doing himself any favours" with his response.
She said: "When you step forward in the midst of a political environment and start giving statements on something dramatic and violent that has happened, you're always leaving yourself open to accusations that you are trying to exploit things politically."
Former presidential candidate John McCain would not say if he thought Mr Romney was wrong but did accuse Mr Obama of running "a feckless foreign policy" that has compromised American influence around the world.
Even if the election is to be dominated by the economy, the American public want a leader who is strong on national security and Mr Obama leads in opinion polls on the issue.