Ralph Nader is launching a third-party campaign for president. The consumer advocate made the announcement Sunday on NBC television's "Meet the Press." He says most Americans are disenchanted with the Democratic and Republican parties, and that none of the presidential contenders are addressing ways to stem corporate crime and Pentagon waste and promote labor rights. Nader also ran as a third-party candidate in the 2000 and 2004 presidential elections. He is still loathed by many Democrats who call him a spoiler and claim his candidacy in 2000 cost the party the election by siphoning votes away from Al Gore in a razor-thin contest in Florida that gave the victory to George W. Bush.