Ralph Nader has formed a presidential exploratory committee, and said in an interview Wednesday that he will launch another presidential bid if he's convinced he can raise enough money to appear on the vast majority of state ballots this fall.

Nader, who ran as an independent candidate in each of the past three presidential elections, told ABCNews.com that he will run in 2008 if he is convinced over the next month that he would be able to raise $10 million over the course of the campaign attract enough lawyers willing to work free of charge to get his name on state ballots.

Nader said he filed papers with the Federal Election Commission and launched a Web Site after Dennis Kucinich, a liberal Ohio congressman, announced his decision to withdraw from the presidential race last week.

He was set to announce that he had formed an exploratory committee Wednesday, even before former Sen. John Edwards made it known that he'd be ending his candidacy. But with Edwards who has made economic populism and ending poverty cornerstones of his campaign leaving the Democratic field, Nader said, he feels his candidacy is more urgent than ever.

"When Kucinich threw in the towel, now you have Edwards gone who's going to carry the torch of democratic populism against the relentless domination of powerful corporations of our government?" Nader said. "You can't just brush these issues to the side because the candidates are ignoring them."

He has harsh words for the leading Democratic candidates, Sen. Hillary Clinton and Sen. Barack Obama, chastising them for failing to advance aggressive plans to tax corporations more fairly, and to fight for a vastly higher minimum wage.

Obama, he said, is a particular disappointment, since his background suggests that he knows the importance of progressive issues yet hasn't fought for them in the Senate.

"His record in the Senate is pretty mediocre," Nader said. "His most distinctive characteristic is the extent to which he censors himself. He hasn't performed as a really progressive first-term senator would."

His "self-censorship," Nader said, "is a reflection of character."

He's no kinder to the Republican frontrunner, Sen. John McCain. "Senator McCain is the candidate of perpetual war," he said.

Nader also rejects the "spoiler" label many Democrats have applied to him since 2000, when his candidacy was blamed in some circles for helping defeat Democratic candidate Al Gore.

"That is the sign of political bigotry," he said. "Why aren't the major candidates spoilers? They represent parties that spoil our electoral system and our government."