DES MOINES (AP) – John Edwards capped his Iowa transformation from 2004’s sunny optimist to 2008’s fiery populist Wednesday night, urging a caucus-eve crowd of 3,000 to take back “our democracy” from greedy corporations.

With rock musician John Mellencamp’s free concert helping fill the Val-Air Ballroom, the former North Carolina senator gave an especially spirited version of his stump speech, tapping a vein of middle-class resentment and worry.

“Corporate greed is robbing our children of the promise of America,” Edwards said to frequent cheers. “It is time for us to fight back.”

Edwards is locked in a tight race with fellow Democrats Hillary Rodham Clinton and Barack Obama in Thursday night’s Iowa caucus, the first voting of the 2008 presidential election. No candidate has spent more time in Iowa, and a strong finish here is crucial to his candidacy.

In recent weeks, Edwards has sharpened his attacks on big oil, pharmaceutical and insurance companies, suggesting he would fight them far more ferociously than would Obama or Clinton. In a modified version of his 2004 “Two Americas” speech, he said 37 million Americans worry each day about how to feed and clothe their families because they live in poverty.

“In America, children living on the streets while the chairmen and CEOs of major companies make millions of dollars?” he asked incredulously. He vowed to make health insurance affordable for all Americans and to reduce dependence on foreign oil.

The night rally, which opened with a half-dozen songs by Mellencamp – including “This is Our Country,” the Edwards campaign theme song – concluded a 36-hour campaign blitz by Edwards and his wife, Elizabeth. Most stops were in much smaller venues than the Val-Air, but each featured Edwards’ stinging rebuke of corporate America.

He likened himself to Theodore Roosevelt, Franklin Roosevelt and Harry Truman, saying all of them took on special interests such as “the big trusts.”

At the Thursday caucus, he told his Val-Air audience, “you’re going to say ‘Enough is enough, we want our country back, we want our democracy back.'”

Many in the ballroom cheered.

“I think he’s got the right stuff,” said Phil Carleson, 56, a high school history teacher. He said Edwards’ charisma reminds him of John F. Kennedy and Bill Clinton.

Shane Harshbarger, 36, said his first choice is New Mexico Gov. Bill Richardson, but Edwards will be his backup if Richardson can’t muster the necessary 15 percent at the Democratic caucus Harshbarger will attend in Des Moines.

Edwards “is a little angry, but I’ll take it,” Harshbarger said. “I like the antiestablishment” message, he said, “because we’ve had too much establishment. That’s Hillary’s problem.”

Mellencamp opened the concert with “Ain’t That America,” and sang another tune with improvised lyrics that poked fun at President Bush’s Iraq and domestic policies.