But with the clock counting down and Edwards running behind in polls in the 10 states that vote Tuesday, the new tact may come too late to help him blunt Kerry's so-far relentless drive toward the Democratic nomination.
Edwards, who relies on his likeability, charm and oratorical flair, has described himself as a "good closer," but the mathematics seem inescapable. So far, Kerry has won 18 of the 20 Democratic contests, and Edwards just one.
Voters consistently give Edwards high marks for his positive message and his approval ratings have topped the field. Yet his sunny side hasn't drawn him enough votes to win anywhere else but South Carolina (search), where he was born.
And that was nearly a month ago.
Checking that happy-face image at the door Sunday, the North Carolina senator bore in on Kerry in Sunday's televised debate in New York.
Edwards rattled off specific voting differences on trade, and accused the Massachusetts senator of having budget-busting proposals and of mouthing "the same old Washington talk." He presented himself as better positioned to protect American jobs and to beat President Bush in the fall.
Of Kerry's claim that their positions, particularly on trade, were nearly identical, Edwards shot back: "He is dead wrong."
"Edwards was much tougher on trade and on portraying Kerry as an insider," said Doug Schoen, an unaffiliated Democratic consultant who was President Clinton's pollster.
"But I don't think it's going to be enough or change the dynamics of the race. And Kerry's responses were just fine," added Schoen. "It probably means that Tuesday will be the effective end of the nominating process."
Kerry parried some of Edwards' thrusts by noting that they are both members of the Senate and both live in Washington — hardly making him the only "insider."
Edwards advisers say he needs to win some states Tuesday, with his best chances coming in Georgia, Ohio and Minnesota. But if he comes up short again, he will come under increased pressure from Democratic leaders to drop out and line up behind Kerry.
A relatively tame debate Thursday in Los Angeles, where the rivals exhibited more common ground than differences, did little to change the contours of the race, raising the stakes for Sunday's encounter.
Edwards' advisers had urged him to be more aggressive now that he is Kerry's chief rival.
With the race essentially a two-man contest, Edwards himself agreed that he needed to do more to draw clearer distinctions between himself and Kerry.
He also boned up on foreign policy, seen as one of his weak areas, by getting a crash course on Haiti on Saturday night as he flew to New York.
In the debate, in which Haiti was a top issue, Edwards noted that Haiti has had 33 previous governments. He also weighed in with specific proposals to ease nuclear tensions with North Korea.
Afterward, Edwards told reporters he was pleased with his performance and said, "I intend to stay in this fight." He was already looking ahead to the March 9 contests in four Southern states — Texas, Florida, Mississippi and Louisiana — where he hopes to do well. "Winning delegates is what matters. I intend to stay in this fight," he said.
But advisers also acknowledged it would be hard for Edwards to continue if he wins nowhere on Tuesday, and said he might seek a graceful way to bow out before the next round.
As of Sunday, for instance, it was undecided where Edwards would spend the night after awaiting election returns in Atlanta on Tuesday. In the past, he has always flown late at night to the next primary state.
Tentative plans are to go to Dallas, but a Kerry sweep could change that.