Independent candidate Ralph Nader (search) conceded on Thursday that he won't win a single state in the presidential election.

"Of course not, the system is rigged," the consumer advocate said when asked if he thought he could carry a state Nov. 2. Nevertheless, Nader is remaining in the race.

Democrats say Nader's candidacy in 2000 cost Al Gore (search) the election as the third-party candidate took votes in states such as Florida and New Hampshire that were decided by razor-thin margins. This year, Nader is on the ballot in more than 30 states, including New York, and is suing for ballot access in several others.

Nader also took a swipe at Democratic vice presidential candidate John Edwards (search), calling him a "sniveling coward." Nader contended that Edwards failed to criticize Vice President Dick Cheney (search) over limiting awards in medical malpractice lawsuits in their debate Tuesday.

Hundreds of prominent Democrats have called for Nader to drop out of the race and urged liberal voters not to support him. Feminist Gloria Steinem (search) and two dozen other women's rights activists signed an open letter on Thursday urging women not to support Nader.

"This election is about ending the reign of George Bush who is intent on dismantling and destroying all that we have worked for years to achieve," the letter says.

"In his current candidacy, Nader seems prepared to sacrifice progress on the issues that women care about — privacy, education, child care, health care, workplace equity and nonviolence at home and abroad," the letter continues.