Consumer advocate Ralph Nader, the perennial third-party candidate, is making his sixth stab at the White House as an Independent candidate this election year.

The lawyer and author, who claims to live on $25,000 a year and give most of his money to his many start-up organizations, has spearheaded numerous consumer protection laws over the decades and was named one of Time Magazine's 100 Most Influential Americans in the Twentieth Century.

Nader's most successful run for the presidency was in 2000 when he challenged then-Gov. George W. Bush and Vice President Al Gore on a debate stage, claiming that the two were "Tweedledee and Tweedledum." The 2000 race was one of the most controversial elections in decades, in part because votes for Nader in Florida and New Hampshire exceeded the difference in votes between the Republican and Democratic candidates—causing some to posit that if Nader wasn't running, Gore would have won those states and thus the election.

Many people called Nader a "spoiler" and blamed him for Gore's loss.

Nader still disputes being blamed for the Democrats' loss, telling Congressional Quarterly in June that he sees the "spoiler" label as "a contemptuous word of political bigotry" that is only attached to the "smaller candidate."

While the 2000 election was a disappointment for Democrats, it was a success for the Green Party. Nader received more than 2.8 million votes, or 2.74 percent of the popular vote. While he didn't quite make the five percent that would have qualified the Green Party for federal public funding in the next election, his success put the party on the ballot in many new states.

Nader was born in 1934 and graduated in 1955 from the Woodrow Wilson School of International Affairs at Princeton University, majoring in East Asian studies. He said his conscience was first stirred by the sight of dead songbirds after the campus sprayed DDT to kill insects.  In 1958, Nader received his law degree with distinction from Harvard University.

Nader entered the public sphere at age 31 with the publication of an article entitled "The Safe Car You Can't Buy." His subsequent book, "Unsafe at Any Speed," documented safety defects in U.S. cars and called attention to the automotive industry's lax safety practices.

In an effort to discredit him, General Motors, hired a detective to investigate his private life. Nader sued GM for invasion of privacy and was paid $425,000 in an out-of-court settlement.

Nader is credited with getting Congress to enact the 1966 National Traffic and Motor Vehicle Safety Act, which created the first mandatory federal safety standards for vehicles. Nader also lobbied for the 1970 Clean Air Act and the 1967 Wholesome Meat Act, which led the U.S. Department of Agriculture inspection of beef and poultry.

In 1969, Nader cofounded the Center for Study of Responsive Law, a non-profit organization that studies and reports on a variety of consumer issues. The employees, mostly young lawyers and law students, became known as Nader's Raiders.

Editor's note: An earlier version of this story contained incorrect information about Ralph Nader's current party affiliation.

-- By Meghann Farnsworth, Online NewsHour