Dead heat going into final debate in Boca Raton battleground

With polls suggesting a dead heat in the US presidential election, Barack Obama and Mitt Romney were cramming yesterday for the third and last debate here in Boca Raton, Florida, this evening that will give each man a critical opportunity to grab the momentum going into the final, frantic two weeks of the contest.

While Mr Romney was already in Florida, itself one of a handful of key battleground states, Mr Obama was huddled with advisers at the presidential retreat in Camp David, Maryland, ahead of the debate. The stakes may be higher for the President, who, since the first debate in Denver, has seen his once handy advantage in polls evaporate.

Moderated by the veteran CBS anchor Bob Schieffer on the campus of Lynn University, the debate will be watched by millions of Americans, only a sliver of whom are still open to persuasion. While the questions will be about foreign affairs, with the Libyan killings, the nuclear stand-off with Iran and the rise of China sure to dominate, both men are likely to pivot frequently to the economy.

In another sign that the race may have become the tightest since George W Bush just squeezed out Al Gore in 2000, an NBC/Wall Street Journal poll saw both men tied at 47 per cent each among likely voters.

Mr Obama will be pressured again to explain the conflicting statements made in the wake of the 11 September attack on the US consulate in Benghazi, Libya, that killed four Americans including Ambassador Christopher Stevens. While it now seems that some in the administration knew from the intelligence services within 24 hours that the attack was the work of militants, some US officials, notably Susan Rice, the US envoy to the UN, continued for days to say it was the work of a mob angered by an anti-Islam video.

Potentially helpful to Mr Romney meanwhile was a report yesterday, denied by both sides, that Iran and the US have agreed to bilateral talks on Iran's nuclear programme, if only because it will act as a reminder that Mr Obama's approach on Iran – trying to engage its leaders and then to pursue sanctions – has still not worked.

On Wednesday, President Obama will begin a frenzied 48-hour campaign blitz that will feature rallies, some in the dead of night in places as far apart as Davenport in Iowa, Denver, Los Angeles and Las Vegas.