After The Times reported on his Facebook remarks, Mr. Loeb deleted them late Thursday night.
“I regret the language I used in expressing my passion for educational choice,” he said in a statement. “I apologize to Senator Stewart-Cousins and anyone I offended. I have taken down the post from Facebook.”
Mr. Klein leads a group of eight Democrats who in 2011 broke away from the main Democratic conference, led by Ms. Stewart-Cousins. Mr. Klein’s group, the Independent Democratic Conference, has in the past sided with the Republicans in the Senate to keep Ms. Stewart-Cousins out of the powerful post of majority leader.
Mr. Loeb has been a prominent player in New York politics, as the chairman of the Success Academy charter school network and as a major political donor. In 2015, protesters objecting to Mr. Cuomo’s ties to wealthy donors marched outside a fund-raiser that Mr. Loeb hosted for Mr. Cuomo at his home in the Hamptons.
Mr. Loeb and his wife have donated more than $170,000 to Mr. Cuomo in recent years, state records show. He has also supported Republicans, with contributions including $500,000 to a super PAC that supported Jeb Bush in 2015, $150,000 to the Republican National Committee that year and $700,000 to a super PAC supporting House Republicans in 2016.
Richard Azzopardi, a spokesman for Mr. Cuomo, said, “We have no connection with these comments whatsoever, and in our opinion they are entirely inappropriate and have no place in the public discourse.”