After weeks of postponing his decision, Nader will appear on NBC's "Meet the Press" to make the announcement, said Linda Schade, a spokeswoman for Nader's presidential exploratory committee.
"He's going to be discussing his role in the presidential election," Schade said of the man whose run for president in 2000 is blamed by many Democrats for tilting a close election in favor of George W. Bush. "He's felt there is a role for an independent candidate to play."
Schade declined to speculate on what the decision would be, but she said Nader would be available for interviews following the television appearance and planned to hold a press conference Monday morning to discuss his communications with the Democratic and Republican parties.
Nader, who turns 70 next week, has said he would base his decision, in part, on whether Democratic and Republican officials respond to his agenda, which includes the need for universal health insurance, a more progressive wage policy and making dramatic reforms to the criminal justice system.
Nader decided in December not to seek the nomination of the Green Party, the insurgent political group he represented in 2000. Green Party officials said at the time they doubted Nader, running as an independent, would get on many state ballots without a party organization and so late in the political season.
Schade said Nader has not begun the process of getting his name on state ballots, which requires garnering thousands of signatures.
In spite of being described by some as a spoiler, Nader for months has been gauging support for another run through an Internet site and exploratory committee. On Thursday, he sent Web site subscribers an e-mail asking them for their thoughts on whether he should seek the presidency.
Nader was on the ballot in nearly every state in 2000 and garnered 2.7 percent of the popular vote. In Florida and New Hampshire, Mr. Bush won such narrow victories that had Gore received the bulk of Nader's votes in those states, he would have won the general election.
His impact on the 2000 race left some feeling bitter, and many former supporters are now urging him not to run. Two former Nader boosters in Colorado have founded a Web site called RepentantNaderVoter.com.
But the Florida vote was so close that even very obscure candidates nay have swung the race. Nader got 97,000 votes in Florida, but Libertarian Harry Brown took 16,000, Reform Party nominee Pat Buchanan received 17,000 and John Hagelin of the Natural Law party had 2,281.
Candidates from the Socialist, Constitution and Workers World parties all took enough votes to make up the Bush-Gore gap.
In an interview late last year, Nader said one reason to run this year would be to "raise the civil liberties issue involving third parties and independent candidates generally." By December, Nader said he had raised about $100,000 to pay expenses for his exploratory phase.
In 2000, Nader criticized both parties for supposedly being dominated by corporate interests.