Democratic presidential candidate Barack Obama leads his Republican rival John McCain by six percentile points, but a recent poll shows that only 47 per cent Americans say they can identify with his background and values compared with 58 per cent saying the same for McCain.

In the latest Wall Street Journal/NBC News poll published in the Journal on Thursday, 47 per cent voters say they prefer Illinois senator Obama to win, while 41 per cent prefer Arizona senator McCain, the same lead Obama enjoyed a month ago.

But noting the low comfort levels with Obama, the Journal said that voters' views of Obama are more fluid than his relatively steady lead indicates. The newspaper went on to comment that this presidential election seems less a contest between two candidates and more a referendum on one of them - Obama.

"The contest parallels in some ways the 1980 race, when voters seemed ready for a change away from Jimmy Carter and the Democrats, but weren't persuaded until late in the race that they could be comfortable with a former actor and unabashed conservative, Ronald Reagan, as commander in chief," the Journal wrote.

"Obama is going to be the point person in this election. Voters want to answer a simple question: Is Barack Obama safe?" Peter Hart, a Democrat who conducts the WSJ/NBC poll along with Republican Neil Newhouse, was quoted as saying by the Journal.

If the answer is yes, then Obama 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, the Journal wrote.

The poll was taken a few days before much of the extensive press coverage of Obama's trip this week to the Middle East and Europe, meant to build his credibility.