WASHINGTON (Reuters) - After weeks of national polls showing the U.S. presidential race as a near dead heat, a survey on Wednesday raised eyebrows by giving President Barack Obama a commanding 13-point lead over his Republican rival Mitt Romney.
The Bloomberg poll showed Obama leading Romney 53 percent to 40 percent among likely voters. Most polls show the two candidates tied, or within a couple of points of one another.
An average of polls compiled by RealClearPolitics.com has Obama leading Romney by 2.2 percentage points, at an average of 46.6 percent to 44.4 percent for Romney.
Bloomberg acknowledged that its survey result varied sharply from other recent polls. Reuters is a competitor of Bloomberg News.
Obama's campaign, which has seen Romney gain on the Democratic president in surveys and fundraising in recent weeks and could use good news, questioned the survey.
"Do I think we have a 13-point lead? No," one campaign official told reporters at a briefing in Washington.
Obama's team anticipates the race will be close because the country is closely split between Democrats and Republicans.
Pollsters said the Bloomberg survey was an outlier, but saw nothing in particular in its samples to explain why it would come out so differently. It is the nature of polling that results occasionally fall outside the mainstream, said Chris Jackson, a pollster at Ipsos, which conducts polls for Reuters.
"It looks on the surface like everything's right, so our guess is it is one of those surveys, that 5 percent, that just gets a weird result," he said.
The Bloomberg survey showed the public giving Obama low marks on his handling of the economy and the deficit, and six out of 10 said the country is headed down the wrong track. But only 39 percent viewed Romney favorably and 48 percent see him unfavorably, which Bloomberg said might reflect damage he suffered during his tough fight for the Republican nomination.
The Bloomberg survey was conducted June 15-18 by Selzer & Co., a respected polling firm in Des Moines, Iowa, based on interviews with 1,002 U.S. adults aged 18 or older.
The respondents were questioned after Obama announced a new policy that would stop deportations of hundreds of thousands of young illegal immigrants, and while Romney was on a bus tour of Midwestern swing states.
Among the respondents, 734 were likely voters, for a margin of error of plus or minus 3.6 percentage points.
Additional reporting by Andy Sullivan, editing by Alistair Bell and Doina Chiacu