Democratic front-runner John Kerry (search) said his commanding showing in Tuesday's Democratic voting across seven states shows he is the candidate who can win across the country and who can defeat President Bush.

Kerry said he was "stunned" by the scope of his victories and called the night a big success, despite finishing second to John Edwards (search) in South Carolina.

"I compliment John Edwards but I think you have to run a national campaign, and I think that's the strength we have shown tonight," Kerry said in an interview with The Associated Press.

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Framing his pitch for the states yet to come, Kerry said in remarks prepared for delivery at his victory party: "Now we will carry this campaign and the cause of a stronger, fairer, more prosperous America to every part of America."

In the seven states holding contests Tuesday, Kerry was the only candidate to stump and advertise everywhere. He watched the election returns in Washington state, turning his attention to a state that -- along with Michigan (search) -- offers the next test in the nominating season on Saturday.

On Tuesday, he sought to elevate his campaign beyond his rivals, beating back competitors in Delaware, Missouri, North Dakota and Arizona.

"It's a huge night. I'm stunned by it. ... It shows strength across the country and across demographics," Kerry told the AP. "It's a statement by Democrats across the country that I am the candidate who can take on George Bush and beat him."

Exit polls showed that in nearly every state, the ability to defeat President Bush was the No. 1 quality voters were looking for, and Kerry was the clear favorite of these voters. In Missouri, he won 75 percent of their votes; in Delaware, 70 percent. In most states, Kerry also was the favorite among those who were looking for a candidate who has the right experience.

He conceded he faces a daunting challenge.

"I know there are powerful interests on the other side -- and the obstacles sometimes seem overwhelming," said Kerry. "But I am ready for this mission."

He congratulated North Carolina Sen. John Edwards on his win in South Carolina, and offered his condolences to Connecticut Sen. Joe Lieberman, who dropped out of the race after coming up winless again, but his main focus was Bush.

"George Bush, who speaks of strength, has made America weaker -- weaker economically, weaker in education and weaker in health care," said Kerry. "Our opponents say they want to campaign on national security. We will not run from that debate -- we welcome it."

Kerry planned to make a redeye flight home to Boston where he would take Wednesday off before plunging Thursday into the campaign for the weekend tests.

He is poised to get the endorsement of the American Federation of Teachers, the country's second largest teachers' union. The 1.2 million-member union's governing board is scheduled to meet Wednesday, but a senior official said Tuesday there was little doubt about the outcome. "It's pretty clear that we're going to endorse Kerry," said the official, speaking on condition of anonymity.

The AFT, roughly half the size of the National Education Association, counts among its members not only teachers, but higher education faculty members, public employees and health care professionals.