As an independent candidate for the White House, Robert F. Kennedy Jr., claims he would be the “best environment president in American history,” drawing on his past as a crusading lawyer who went after polluters in New York.
But dozens of Mr. Kennedy’s former colleagues at the Natural Resources Defense Council are calling on him to withdraw from the race, in full-page advertisements sponsored by the group’s political arm that are expected to appear in newspapers in six swing states on Sunday.
Separately, a dozen other national environmental organizations have issued an open letter calling Mr. Kennedy “ a “dangerous conspiracy theorist and a science denier” who promotes “toxic beliefs” on vaccines and on climate change.
People involved in both efforts maintain that Mr. Kennedy cannot win the presidency but could siphon votes away from President Biden and help elect former President Donald J. Trump, who has called climate change a hoax and promised to unravel environmental laws and policies.
“A vote for RFK Jr. is a vote to destroy that progress and put Trump back in the White House,” says the newspaper ad that will run in Georgia, North Carolina, Nevada, Michigan, Wisconsin and Pennsylvania. Signatories include John Hamilton Adams, who co-founded the Natural Resources Defense Council and hired Mr. Kennedy in the 1980s, as well as past presidents and the group’s current president. They implore Mr. Kennedy to “Honor our planet, drop out.”
Mr. Kennedy was a senior attorney for the Natural Resources Defense Council for about 28 years, stepping down in 2014.
In a telephone interview on Thursday, Mr. Kennedy shot back against the idea that he might bring Mr. Trump back to the White House.
“President Biden does not need my help to lose to Donald Trump,” Mr. Kennedy said. He avoided directly addressing the actions of Mr. Adams and other former colleagues, saying only that he and his mentor “disagree with each other on politics.”
Instead Mr. Kennedy criticized Mr. Biden as well as the environmental movement, which he said “is making a mistake to settle for crumbs that have been given to us by the Biden administration.”
Former colleagues in environmental circles were unvarnished in their assessments of Mr. Kennedy.
“The Bobby I knew is gone,” said Dan Reicher, a senior energy researcher at Stanford University’s Woods Institute for Environment. Mr. Reicher worked with Mr. Kennedy at N.R.D.C. and said he had a decades-long personal friendship with Mr. Kennedy, including paddling rivers together in the United States and Chile.
Gina McCarthy was the administrator of the Environmental Protection Agency under President Barack Obama and then became president of N.R.D.C. during the Trump administration, only to return to national service as Mr. Biden’s climate adviser until last year.
“If folks remember him as an environmentalist, he is no more,” she said about Mr. Kennedy. “He’s against science, he’s against vaccines, he talks jibber jabber on climate. I don’t know what he stands for.”
Mr. Adams said in a statement: ”I mentored Bobby as a young environmentalist. I do not recognize the person he has become. His actions are a betrayal to our environment.”
The rebuke from Mr. Kennedy’s professional colleagues comes after his brothers and sisters and other members of the Kennedy family endorsed President Biden at a campaign rally in Philadelphia on Thursday. Mr. Kennedy is a nephew of former President John F. Kennedy and a son of the former attorney general and presidential candidate Robert F. Kennedy. Family members have said they are concerned that Mr. Kennedy could tilt the race to Mr. Trump.
Allies of Mr. Trump have been discussing ways to elevate third-party candidates like Mr. Kennedy in battleground states to divert votes away from Mr. Biden. They are looking to underline Mr. Kennedy’s background as an environmentalist in the hope of peeling away some progressive voters frustrated by the fact that under Mr. Biden, the country has produced record levels of oil and gas.
“The path to victory here is clearly maximizing the reach of these left-wing alternatives,” Stephen K. Bannon, the former White House chief strategist who also served as Mr. Trump’s campaign chairman in 2016, told The New York Times earlier this month.
Mr. Kennedy’s views on climate change are unconventional. He agrees with the overwhelming scientific opinion that carbon dioxide and methane, two greenhouse gases, are heating the planet, and that the evidence is visible. “All of my senses are telling me that the warming is occurring,” he said in a video he posted to X in July.
But in the same video, he also said that a “war on carbon” was not the answer and that “this crisis is being used as a pretext for clamping down totalitarian controls.” He said that the actors behind the clampdown were “the intelligence agencies, the World Economic Forum, the billionaire club at Davos,” and that their goal was to make the rich more wealthy. But moments later, he said that free markets would solve the climate crisis.
Mr. Kennedy said he opposed federal subsidies for carbon capture and storage, a technology to capture greenhouse gas emissions from power plants or industrial processes before they reach the atmosphere, where they drive global warming. Mr. Kennedy called it a “useless and huge boondoggle to the industry” and criticized Mr. Biden for agreeing to include those subsidies in the 2022 Inflation Reduction Act, the president’s landmark climate law.
Many environmental activists are also opposed to carbon capture technology because they want the nation to stop burning fossil fuels and instead switch to wind, solar and other nonpolluting energy sources.
But Mr. Kennedy’s agenda does not include any clear policies to cut greenhouse gas emissions.
On Thursday he said eliminating subsidies for fossil fuels and tougher enforcement of existing laws like the Clean Water Act and the Clean Air Act would be sufficient to fight climate change. President Biden has tried three times to eliminate fossil fuel subsidies, and each time, Congress has restored them. And in recent rulings, the conservative majority on the U.S. Supreme Court has limited the Biden administration’s ability under existing laws to regulate greenhouse gases.
Mr. Kennedy also said the environmental movement was making “a huge tactical error” in focusing on climate change instead of environmental issues that are less divisive.
He accused Mr. Biden of turning his back on the environment by approving the Willow project, an $8 billion oil drilling project in Alaska; for overseeing record oil and gas production; and for signing the Inflation Reduction Act, which ensures continued offshore oil drilling.
“It’s hard to understand how the environmental movement is now saying that this is OK,” Mr. Kennedy said. “I think we need a bigger vision for the environment.”
Manish Bapna, the president of the Natural Resources Defense Council Action Fund, the political arm of the nonprofit environmental organization, noted that Mr. Kennedy had also criticized the federal subsidies that jump-started domestic manufacturing of electric vehicles and batteries and solar and wind production in the United States.
“Voters who care about the environment shouldn’t be fooled,” Mr. Bapna said.
Mr. Biden has enacted the most aggressive climate agenda of any president. In addition to the Inflation Reduction Act, which is providing more than $370 billion for clean energy over the next decade, he is limiting emissions from automobiles, is poised to cut carbon pollution from power plants and has reined in future oil and gas drilling by limiting the available tracts of land and water that companies can lease.
The political ad does not discuss Mr. Kennedy’s record as a lawyer who helped clean up the Hudson River and started a global movement to protect waterways.
Mr. Kennedy was named a hero of the planet by Time magazine in 1999 for his work with the Riverkeeper organization, among the groups credited with cleaning up the Hudson. As a founder of the Waterkeeper Alliance, he successfully fought to close a New York landfill that was contaminating the water supply and helped defeat dams in Chile and Peru.