WASHINGTON — It was early Wednesday morning, and Chief Justice John G. Roberts Jr. had had enough. He had been listening to increasingly acid exchanges at the impeachment trial of President Trump, and he was ready to chastise the House managers and the president’s lawyers.

And he did it in the characteristically mild and evenhanded tones he uses when he presides over the Supreme Court.

“I think it is appropriate at this point for me to admonish both the House managers and the president’s counsel in equal terms to remember that they are addressing the world’s greatest deliberative body,” Chief Justice Roberts said.

The remarks highlighted the chief justice’s uncomfortable position as he begins fulfilling his constitutional obligation to preside over presidential impeachment trials. He finds himself in an unwelcome spotlight, subject to intense and unfamiliar scrutiny. The role is limited, and there is no particular reason to think he wants to test its limits.