Former Green party presidential candidate Ralph Nader says that Sens. Elizabeth Warren (D., Mass.) and Bernie Sanders (Socialist, Vt.), would make a “very powerful ticket” for Democrats in the 2020 general election. Mr. Nader adds that such a combination, combined with aggressive Democratic party efforts to keep Greens off the ballot, would make it hard for a Green party candidate to attract many votes in November of next year.

Mr. Nader, who first gained fame as an anti-corporate activist in the 1960s, calls Sens. Warren and Sanders the “strongest team” for Democrats in 2020 and says it’s “absolutely accurate” to see their campaigns as the legacy of his own multiple runs for President.

Mr. Nader is perhaps best known for his 2000 campaign, which some Democrats blame for siphoning votes away from then-Vice President Al Gore and costing him the election against then-Gov. George W. Bush (R., Texas). Mr. Nader ran as a Green party candidate that year in part because he believed that Mr. Gore and his Democratic party colleagues were insufficiently committed to the environmental agenda.

As for candidates seeking the 2020 Democratic nomination, Mr. Nader says it’s “too bad” that Sens. Warren and Sanders are “pitted against each other” since they are both advancing many of Mr. Nader’s views. “They can flip a coin” to decide who leads the ticket, says the former Green candidate, adding that both Ms. Warren and Mr. Sanders are “articulate” and “pretty clean.”

Considering the messages of the current campaigns Mr. Nader jokes that he could “almost accuse” Mr. Sanders of “plagiarism” if the Vermonter hadn’t been making such arguments for decades. And the anti-business crusader seems no less enthusiastic about Ms. Warren. “I think they complement each other,” he says.