The resignation on Sunday of Mohammad Javad Zarif, who had been appointed vice president for strategy and had led a search committee for cabinet nominations, shocked Iran’s political circles. He had been a prominent face of Mr. Pezeshkian’s campaign, traveling across the country and telling voters to give change a chance. Now, he was abandoning the government in a public display of deep divisions before it was even formed.

In a post on his Instagram account, Mr. Zarif said it had become clear to him that he could not bring about the kind of domestic change that people had expected.