Senator John Kerry has cruised to victory in the latest US state caucus to choose a Democratic challenger to President George W Bush.
Mr Kerry faces tougher tests in the south
With half the ballots counted in Maine, Mr Kerry had 45% of the vote, far ahead of the other five candidates.
On Saturday, the senator scooped Washington and Michigan states, and has won 10 out of 12 contests so far.
In a sign of confidence, Mr Kerry on Sunday rounded on Mr Bush after the president defended the war on Iraq.
Speaking in an hour-long TV interview, the president said the conflict was a "war of necessity" because deposed Iraqi leader Saddam Hussein had "the ability to make weapons" of mass destruction.
Looking like he was gearing up for a November showdown with Mr Bush, decorated Vietnam veteran Mr Kerry told the president to tell the truth.
"The problem is not just that President Bush is changing his story now... it is that it appears he was telling the American people stories in 2002," as the US prepared for war, he said.
South tougher test
In a statement, Mr Kerry said the voters of Maine "have sent a message that George Bush's days are numbered and change is coming to America".
While he is clearly the front-runner for the Democratic nomination, Mr Kerry is expected to face a tougher test when the campaign moves southward on Tuesday.
His two Southern rivals - Wesley Clark and John Edwards - have been focusing the campaign efforts on Virginia and Tennessee, where Mr Kerry is considered more vulnerable.
Last week, Senator Edwards won in South Carolina, while Wesley Clark took Oklahoma.
On Sunday, Mr Clark said his team "expect to be there on Super Tuesday", when 10 states pick a candidate, while Senator Edwards said he would stay in the race for the long haul.
"Even after Wisconsin, which is still a little over a week away, something like 75% of the delegates are left to be chosen," Mr Edwards said.
One-time front-runner, former Vermont governor Dean, has said he will withdraw from the race if he does not win the Wisconsin ballot on 17 February.
Mr Dean suffered a new blow on Saturday when the head of a major union - the American Federation of State, County and Municipal Employees - withdrew his support.
Twenty-four delegates to the Democratic national convention that select the party's presidential candidate in July were at stake in Maine.
Mr Kerry also has more than twice as many delegates as his
closest pursuer, with 411 to Mr Dean's 175, according to a tally prior to allocation of Maine's delegates.
It takes 2,162 delegates to win the nomination.