The poll conducted for the Wall Street Journal/NBC News found that 47 per cent of respondents favour Obama against 41 per cent for McCain. The lead is same that the African-American Senator enjoyed a month ago.
The margin of error is plus or minus 3.1 percentage points.
Asked whether they could identify with the background and values of the two candidates, 58 per cent said they could identify with McCain on that account, while 47 per cent said the same about Obama.
More than four in 10 said the Democratic contender does not have values and background they can identify with.
Those findings suggest voters' views of Obama are more fluid than his relatively steady lead indicates, the pollsters said.
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"Obama is going to be the point person in this election," says pollster Peter Hart, a Democrat who conducts the Wall Street Journal/NBC News poll along with Republican Neil Newhouse. "Voters want to answer a simple question: Is Barack Obama safe?"
If the answer is yes, then Obama, who is aspiring to be the first black President of America, stands to benefit further from a favourable environment for Democrats. If no, McCain is seen by a wide swath of Americans as a safe, well-qualified potential commander-in-chief.