Barack Obama's campaign to become the Democratic candidate for American President gathered momentum as he won the party's vote in Maine.

The defeat came as a heavy blow to his rival Hillary Clinton because the voters in Maine are mostly older, blue-collar workers and those are the people that have shown her support in the campaign so far.

Mrs Clinton responded by replacing her campaign manager Patti Doyle with her long-term aide Maggie Williams.

Mr Obama also won polls in Louisiana, Nebraska, Washington state and the US Virgin Islands over the weekend.

He said: "We have now won on the Atlantic coast, we've won on the North Coast, we've won on the Pacific Coast, and we've won in between those coasts."

Mr Obama's victory may be partly explained by the selection system in Maine, which is a caucus state where candidates are chosen after private meetings, rather than by elections in primary states.

He has won almost all of the caucus states and so far he has the support of 741 delegates, compared to Mrs Clinton's 912. The Democrats' nominee will be the first person to earn the backing of 2,025 delegates.

Mrs Clinton will face a critical test later this week at primaries held in Washington DC, Maryland and Virginia.

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