JACKSONVILLE, Fla. (Reuters) - One speech may not a campaign make, but John Kerry and his top advisers are pumped up and in "a fighting mood" after the Democratic candidate's aggressive attack on President Bush's handling of Iraq.

The Massachusetts senator, lagging in opinion polls six weeks before the Nov. 2 election, seems to have kicked a habit of pulling his punches at the last minute and showed a new willingness to mix it up with his Republican rival.

From a scathing address in New York on Monday detailing Bush's "arrogance and outright incompetence" on Iraq, to a Democratic fund-raiser and on to a Tuesday morning television talk show where he charged that the president was "in denial," Kerry seems to have found a new lease on political life.

"These guys, they've got me in a fighting mood," Kerry said to roars of approval at a Monday night campaign rally in New York.

"Many people have said this was a speech you needed to give," said Mike McCurry, a Kerry adviser and former White House spokesman for President Bill Clinton. Several Democrats outside the campaign called it a turning point that would force Bush to play defense.

Republican campaign officials saw the speech in a different light as just containing "new contradictions and more confusion."

"My opponent has taken so many different positions on Iraq that his statements are hardly credible at all," Bush told reporters in New York where he was addressing the United Nations.

Kerry staff members were delighted at the newspaper and television coverage devoted to their boss's stinging critique of Bush's "colossal failures of judgment" in the run-up to the war and its aftermath.

"He rocked, didn't he," the candidate's wife Teresa Heinz Kerry declared at a New York reception on Monday. "There's a time for everything and it was time for him to take off the gloves."

It was a welcome change for the Democratic faithful who privately feared their candidate lacked fire, and vindication and for a cadre of new advisers who urged Kerry to land some punches instead of simply shadow boxing with Bush.

"It was a very important speech, he was very clear, he feels very good about it and so do we," Kerry spokeswoman Allison Dobson said on Tuesday.

A senior Kerry aide portrayed the Iraq speech as a kind of catharsis for voters as well as the candidate, who has struggled with the issue throughout the spring and summer.

"I think people responded to the fact that someone finally told the hard truths," the aide said. "The White House's weak response was telling. They didn't challenge a single assertion he made about the situation on the ground."

But Kerry has often wrestled with just how hard to hit. His tendency was to retreat altogether from some of the harsher rhetoric that appears in his prepared remarks or to soften it.

Instead of accusing Bush of living "in a fantasy world of spin" on Iraq, he told a National Guard conference the president was dwelling in "a different world of spin."

An advance text of a fiery address full of biblical allusions before a Baptist convention warned blacks to beware of Bush's overtures, comparing the president to a wolf in sheep's clothing. Instead, Kerry described him as a "false prophet."