He broke with the left over its criticism of Israel and what he saw as its anti-Americanism. But he also became a critic of Donald Trump.

Sol Stern, a public policy apostate and provocateur who evolved from an ardent leftist in the 1960s to a self-described moderate conservative, but who broke with the Republican establishment over its unconditional embrace of Donald J. Trump, died on Friday at his home in Manhattan. He was 89.

His wife, Ruthie Stern, said the cause was cancer.

As a writer, an editor and an adviser to government officials, Mr. Stern remained an enrolled Democrat, although he voted for John McCain, the Republican candidate, over Barack Obama for president in 2008. He was known for his largely nonideological judgment and his willingness to change his mind when he believed his prescriptions for society’s ills had been overtaken by factual evidence.

In the 1990s, disillusioned with how his two sons