Mr. Herbert, who started his Times column in 1993, was known for his combative style, blunt language and progressive politics. In a message accompanying the announcement, Mr. Herbert, who is 66, said he was eager to move on to a new form of writing.

“The deadlines and demands were a useful discipline, but for some time now I have grown eager to move beyond the constriction of the column format, with its rigid 800-word limit, in favor of broader and more versatile efforts,” he said. “So I am leaving The New York Times and the rewards and rigors of daily journalism with the intent of writing more expansively and more aggressively about the injustices visited on working people, the poor and the many others in our society who find themselves on the wrong side of power.”