R.F.K. Jr.’s Environmental Colleagues Urge Him to Drop Presidential Bid

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.