Mitt Romney has doubled his lead in a new national poll just hours after the final presidential debate in Boca Raton, Florida.

Just two weeks to go until election day it is unclear whether President Barack Obama will be able to make up the gap.

Mitt Romney held a four-point lead in the Rasmussen tracking poll released on Tuesday, with 50% of the vote compared to 46% for Barack Obama. In Monday’s poll he led by two points.

In addition, Mitt Romney’s lead was five points in swing states and as many as nine points among self-declared independent voters.

The poll was released just a few hours after the third and last debate of the presidential election campaign, which saw the two candidates clash over foreign affairs in Boca Raton.

Barack Obama showed off his foreign-policy experience, repeatedly patronizing his opponent as he accused him off being “all over the map” on how to deal with the world, even describing him as “wrong and reckless”.

But Mitt Romney held his own in the face of Barack Obama’s sustained assaults, working hard to establish his credentials as a sober and steady statesman with an obviously well-briefed analysis of world matters, from Iran to Poland to Mali.

The two bitter rivals were meeting for the final time at Lynn University in Boca Raton with all to play for in a neck-and-neck race for the White House.

CNN’s survey of debate-watchers showed that 48% considered the President the winner, with 40% favoring Romney and 12% undecided. A CBS poll had Barack Obama in front with 53% compared to just 23% for Romney, with 24% on the fence.

The Rasmussen Reports poll released on Tuesday recounted only the results of surveys conducted before the debate, so it is not yet known whether either candidate will receive a boost from the evening.

Mitt Romney has doubled his lead in a new national poll just hours after the final presidential debate in Boca Raton

One contest Barack Obama undoubtedly won was that of loquaciousness – the President spoke for 41 minutes and 42 seconds, 35 seconds longer than Mitt Romney. The Democratic candidate had the majority of speaking time in all four presidential or vice-presidential debates this year.

It was Barack Obama who appeared to be the challenger at times – a clear sign that he fears his re-election hopes are slipping away from him – hammering away at Mitt Romney, trying to belittle him and all but calling him a liar.

Mitt Romney tried to remain above the fray and appeal to moderate and undecided voters. He was noticeably less tetchy than in the bad-tempered second debate in Hempstead, New York.

But Mitt Romney hit home with a precise attack on Barack Obama’s “apology tour” of the Middle East in 2009, which seemed to rile Obama visibly. He said that the President had said he was sorry the U.S. had dictated to countries, adding: “Mr. President we have not dictated to other nations, we have freed other nations from dictators.”

The Romney campaign appeared confident in the aftermath of the debate, arguing that Barack Obama was “shedding voters” and was “trying to manage the rate of decline” in support ahead of election day.

“We entered this debate in a good position and we leave it in a stronger position,” said strategist Stuart Stevens.

“Whatever is that intangible quality of being presidential and who you would trust, Governor Romney had it more than the President.”

Speaking about Barack Obama’s performance in Boca Raton, Stuart Stevens added: “It was not the demeanor you would expect of a President. He came in with a bunch of political talking points like a young fresh graduate of a spin class trying to come off with these points.”

But the President’s campaign manager Jim Messina described Mitt Romney as “unsteady”, adding that he “did not look like a commander-in-chief. He did not pass the test and that’s a very bad moment for the Romney campaign”.

Jim Messina continued: “The contrast tonight was between a strong and steady President and an uncertain Romney and that’s how incumbent presidents get re-elected.”

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