"If it's a choice between Hillary Clinton and Donald Trump, do you see much difference between the two?" CNN's Anderson Cooper asked Nader Wednesday on "AC360."
"Yeah, of course there's a difference, but they both flunk," he said.
"I mean here you have a failed gambling czar who became a corporate welfare king that's cheated his way to a billion dollars by every of his business operations ... I mean he's cheated his workers, consumers, creditors, suppliers, taxpayers -- and he's the nominee for the Republican Party," Nader said.
Clinton, he said, is "more Wall Street and more war."
"I mean, she's a hawk that actually scares the generals," Nader said.
Nader said that he believes the Green Party has the best platform compared to the other parties in the election.
"There are third parties and they are write-ins. I think the Green Party has, by far, the best platform over the years," Nader said. "So they do have some choice if they don't want to write their name in, I always favor a none of the above on every ballot line."
Nader, who some liberals blamed for spoiling the 2000 election when Democrat Al Gore won the popular vote but lost the Electoral College and the presidency to George W. Bush, denied that third party candidates harm electoral outcomes.
"You'll notice that the two major party candidates never call each other spoilers. It's only directed a third party candidate who's considered someone that take votes away," Nader said. "Well, if we have an equal right to run for the election under the Constitution and use our First Amendment right, then we're all trying to get votes from one another and we're all trying to either spoil one another or none of us are spoilers."
"That's why I call the designation of spoiler is a bigoted word backed up by ballot obstacles and all kinds of discriminatory barriers that third parties are subjected to unlike any other Western nation," he added.