In more bad news for Hillary Clinton, Barack Obama has for the first time emerged as the favourite among Democratic voters in the White House race while the vitriolic campaign intensified with a fresh slanging match on a photograph of Obama in a traditional African dress.

A CBS News/ New York Times Poll has found that Obama, who is leading in the delegate race, had 54 per cent backing of democratic primary voters as opposed to 38 per cent of Clinton, who faces a do-or-die battle in the March 4 contests in Ohio and Texas.

The fresh setback came as polls indicated that the 60-year-old former first lady was fast losing her turf in the two states to the African-American. In January, the Clinton was leading by a 15-point margin nationally. Today/Gallup Poll released on Monday showed 51 per cent for Obama to 39 per cent for Clinton.

With a tough battle ahead, the vitriolic campaign was fuelled again by a photograph of Obama wearing a white turban and a robe during a 2006 visit to Kenya which appeared on the Internet.

The photo was first circulated by Internet gossip columnist Matt Drudge in The Drudge Report which said it purportedly came from a Clinton staffer through an e-mail but the New York Democrat dismissed the allegation as "laughable".

The Obama camp was not amused with manager David Plouffe accusing Clinton's campaign of "the most shameful, offensive fear-mongering we've seen from either party in this election".

But the Clinton surrogates hit back forcefully terming it a strategy by Obama camp to distract the voters from real issues through a "divisive" campaign

"Enough. If Barack Obama's campaign wants to suggest that a photo of him wearing traditional Somali clothing is divisive, they should be ashamed. Hillary Clinton has worn the traditional clothing of countries she has visited and had those photos published widely," campaign manager Maggie Williams said in a statement.

Clinton said she was not aware of the photograph and instead accused his rival of a trying to cover up for inadequacies in his plans for the country and the world.

"I know nothing about it," Clinton said to an ABC news affiliate.

"This is in the public domain.  But let's just stop and ask yourself: 'Why are you -- why is anybody concerned about this?" she said.

"This one more attempt by my opponent's  campaign to change the subject. From his health-care plan that won't cover everybody, from an economic plan that won't produce jobs, and from a record that is pretty thin when it comes to national security and standing up for our country around the world," Senator Clinton said.

But Senator Obama maintained that voters are "saddened" by this kind of politics.

"The notion that the Clinton campaign would be trying to circulate this as a negative on the same day that Senator Clinton was giving a speech about how we repair our relationships around the world is sad," he said.

With 11 straight wins, Obama leads with 1,362 delegates. Clinton has 1,266.5, getting the half-delegate from the Democrats Abroad primary. It will take 2,025 delegates to secure the Democratic nomination at the party's convention in late August in Denver.

Republican John McCainn has almost sealed his nomination for the November Presidential election