NEW YORK, USA (AFP) — If President Barack Obama wins re-election in three weeks time, he will begin his second term heavily in debt to Bill and Hillary Clinton, one-time tormentors turned power-couple protectors.

As Obama headed to New York for a crucial debate against resurgent Republican challenger Mitt Romney, the Clintons, the dominant Democrats of the last 20 years, were again stealing the headlines.

Taking a hit Romney may have lined up for Obama, Secretary of State Hillary Clinton took the blame Monday for shortcomings in the handling of an attack on the US consulate in Benghazi that killed four Americans.

Her comments, in Peru, may have taken some of the sting out of Romney’s possible attack and marked the administration’s most emphatic effort to quell a political storm over Libya that threatens to hurt Obama’s re-election bid.

The 11th-hour pre-debate intervention also prompted new questions over the motives of the Clintons in embracing their former foe, including: will the bill come to Obama in the form of backing a “Hillary 2016” White House bid?

Republicans, though, are not done with this year, and continued to pin the Benghazi blame on Obama, recalling the ad Clinton ran in the 2008 Democratic primary, questioning whether her relatively inexperienced rival was ready for a national security crisis.

“I think it’s the 3:00 am call, right? I mean, the buck stops at the White House. That’s what Hillary Clinton said back in 2008. She’s saying something differently today,” Republican party chief Reince Priebus told MSNBC.

With a wink and a smile Clinton often declares she will be “out of politics” early next year, but her enduring popularity makes her decision to accept the Benghazi fallout for Obama on the eve of a make-or-break debate a distinctly political act.

Bill Clinton, the 42nd President, was meanwhile waging another tussle for his Democratic successor, rebutting Romney’s tax policy in the folksy drawl he used in last month’s acclaimed Democratic National Convention speech.

In a campaign video, the snowy-haired veteran made the kind of forceful case that was beyond Obama in the first debate — a point not lost on one of the ex-president’s chief antagonists, former Republican House speaker Newt Gingrich.

“You have to admire the Clintons. Bill and Hillary Clinton have done more to re-elect Barack Obama than Barack Obama has,” Gingrich told Fox News.

Bill Clinton, whose economic credibility is vital for Obama, will hit the campaign trail again for Obama in Ohio and Wisconsin this week.

The heft of the Clinton effort for Obama is all the more remarkable considering the bitterness spawned by his 2008 primary battle with Hillary.

Obama, whose campaign was once dismissed as a “fairy tale” by the former president, effectively blocked what would have been a remarkable Clinton restoration, eight years after they left the White House.

Clinton was also furious when some Obama supporters said he had played the race card.

The thaw began when Obama shocked his inner circle by asking Hillary, then a New York senator, to join his “team of rivals” cabinet.

But even now, few people suggest that the Clintons and Obama are friends, though the president and his secretary of state and her husband show mutual respect.

As for the Clintons’ motives, they remain open to debate.

Given Hillary Clinton’s narrow defeat to Obama and support of 18 million primary voters in 2008, talk of a possible second presidential campaign frequently churns in the Washington rumour mill.