Barack Obama last night easily won Mississippi's Democratic primary, his latest victory in a string of racially polarised contests in America's Deep South and after a day when a new race row erupted in his nomination battle with Hillary Clinton.

Mr Obama won the Magnolia State with over 90 per cent support from African Americans, but with only about one-quarter of the white vote, extending a pattern that bought him him resounding victories in earlier primaries in South Carolina, Alabama, Georgia and Louisiana.

His victory, with 33 delegates up for grabs, was widely expected, as was his win in Wyoming's caucuses on Saturday. Yet he remains locked in the extraordinarily tight and unpredictable nomination battle with Mrs Clinton, which now stretches for six weeks until the next contest in Pennsylvania on April 22, and possibly all the way to the nominating convention in Denver in late August.

Mr Obama leads Mrs Clinton among elected delegates and it appears almost impossible for her to erase that advantage by the time the primary and caucus contests have finished in June, despite her momentum-building wins in Ohio and Texas last week.

As the results came in from Mississippi a deal appeared to be nearing over re-running the primary votes in Michigan and Florida, a move that the Clinton campaign has been agitating for. Although the two states have already voted, they were stripped of their delegates because they defied the national Democratic party rules by moving their contests up the nominating calendar. Mrs Clinton won both original votes, but Mr Obama was not even on the ballot in Michigan and did not campaign in Florida.

Mr Obama appears highly likely to win more elected delegates than Mrs Clinton. But the former First Lady hopes that if she can win Pennsylvania - where she is favoured because of its heavy white, blue collar voting base - in addition to rerun contests in Michigan and Florida, she has a good chance of catching the Illinois senator in the popular vote. She hopes to combine that with the argument that she has won far more major and battleground states, such as Ohio and California, to sway the party's superdelegates, the nearly 800 elected officials and party leaders who now appear most likely to determine the contest.

After his victory in Mississippi, Mr Obama said he was interested in seeing a "fair settlement" in Florida and Michigan. The Democratic party appeared close to allowing the states to vote again, this time with a postal ballot. Referring to his victory in Mississippi, Mr Obama said it was, "just another win in column". He added: "We are getting more delegates. We are making the case for change in each state."

The Mississippi vote came after a day in which Geraldine Ferraro, the Democrats’ 1984 vice-presidential nominee and a supporter of Hillary Clinton, ignited a firestorm by saying Barack Obama had been successful only because he is black man.

“If Obama was a white man, he would not be in this position,” Ms Ferraro, 72, said. She added: “And if he was a woman of any colour he would not be in this position. He happens to be very lucky to be who he is. And the country is caught up in the concept.”

Mr Obama responded: “I don’t think Geraldine Ferraro’s comments have any place in our politics or in the Democratic Party. They are divisive.” His foreign policy adviser, Susan Rice, an African American, called them "outrageous and offensive".

Last week another foreign policy adviser to Mr Obama, Samantha Power, was forced to quit after calling Mrs Clinton a “monster”. Dr Rice said Ms Ferraro’s comments were “far worse”.

Mrs Clinton last night said of Ms Ferraro's comments: "I do not agree with that." She added: "It's regrettable that any of our supporters — on both sides, because we both have this experience — say things that kind of veer off into the personal."

Mr Obama's aides said it was an insufficient condemnation and accused the former First Lady's campaign of an "insidious" pattern of underhand racist attacks on her rival.

Ms Ferraro, chosen by Walter Mondale to be his running mate in 1984 when they lost in a landslide to Ronald Reagan and George Bush Senior, insisted her comment was not racist. She said she was “absolutely offended” by the angry response and blamed David Axelrod, Mr Obama's chief strategist, for stirring up anger.

Democratic elders are becoming increasingly concerned that as the nominating battle breaks along race, class and gender lines, the party is in danger of an acrimonious split that could jeopardise its chances of recapturing the White House in November.

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