"Don't conservatives, in contrast to corporationists, want movement toward a safe environment, toward ending corporate welfare and the commercialization of childhood? Let us not in this campaign prejudge any voters, for Green values are majoritarian values, respecting all peoples and striving to give greater voice to all voters," Nader said in his acceptance speech at the Green Party's national convention in Denver.
Nader easily defeated challengers Jello Biafra and Stephen Gaskin for the nomination.
For his vice presidential running mate, Nader chose Winona LaDuke, an Ojibwe activist from the White Earth Reservation in northern Minnesota.
In a wide-ranging news conference, Nader criticized the Republicans and Democrats for keeping third parties out of the all-important fall presidential debates. Currently, candidates must reach a 15 percent threshold in certain national polls in order to qualify for the televised debates.
He accused Democrat Al Gore and his Republican rival, Texas Gov. George W. Bush, of trying "to keep the debates narrow, the issues few and the information limited."
"This is the people's election. They should seize it back from the Democratic and Republican parties and their corporate sponsors," Nader said.
The longtime consumer activist, who's made a career of tormenting corporate fat cats and taunting political bigwgs, could have a more profound impact on the race for the White House than anyone would have predicted a few months ago. Though his support remains in the single digits, it could be enough to influence the results in several states, including a number of key midwestern swing states and California.
That could spell trouble for Gore, whose campaign is already staggering after the recent resignation of chairman Tony Coelho and the news that a Justice Department prosecutor wants a special counsel to investigate Gore's role in a 1996 fund-raising scandal.
Nader, whose support comes almost entirely from Democrats and independents, said it "really doesn't matter" if his bid costs Gore the election, as long as the two parties get the message and listen to the millions of disaffected voters who did not vote in the last election.
"The official word from the Gore campaign toward this campaign is they are not losing any sleep over it, to which I reply, 'Slumber on Al Gore, slumber on,'" Nader told CBS News Correspondent Phil Jones.
Nader has consistently ridiculed the vice president and tried to convince voters that Gore and Bush are essentially identical on key issues like trade and the environment. And with one prominent Democratic constituency - organized labor - he appearto have had some success.
After a meeting with Nader last week, Teamsters President James P. Hoffa said, "There is no distinction between Al Gore and George W. Bush when it comes to trade."
Hoffa, who represents 1.4 million Teamsters, added that Gore was "wrong on trade" and said, "We agree wholeheartedly with what Mr. Nader has said."
Nader has argued vociferously against the China trade deal, which passed the House last month, and which both Gore and Bush support.
While acknowledging that his campaign is a long shot, Nader insisted he has a chance to win. If the Republicans and Democrats think he is joking, he said, they should talk to the disaffected Minnesota voters who made former professional wrestler Jesse Ventura their governor.
Nader said mainstream politics are moving toward Green Party values, and he cited examples: voters frustrated with traffic jams, concerned about pollution and angry with their lack of a voice in the political system.
"This is such mainstream stuff," he said in an interview with wire service reporters.
Recent polls show Nader surging ahead of Reform Party contender Pat Buchanan as the most popular third-party challenger in the campaign, but still far behind Gore and Bush. A Newsweek poll on Sunday showed Nader with 3 percent and Buchanan 2 percent nationwide, compared to Bush and Gore, who were in a statistical dead heat at 42 percent and 40 percent, respectively. The poll had a 4 percentage point margin of error.