Senate Democrats on Wednesday opened a confirmation hearing for Deputy Secretary of State John J. Sullivan as ambassador to Russia with questions about why he recalled the former ambassador to Ukraine, Marie Yovanovitch, and did not stand up more forcefully for the foreign service.

Sullivan, responding to sharp questions by Sen. Robert Menendez (N.J.), the top Democrat on the Foreign Relations Committee, agreed that Yovanovitch had “served capably and admirably.”

But Secretary of State Mike Pompeo, he said, told him “the president had lost confidence with her,” and he was designated to deliver the news to her. Pompeo, he indicated, declined to specify any further reason in response to Sullivan’s appeal.

Yovanovitch was the target of a smear campaign by allies of President Trump because she did not subscribe to conspiracy theories about Ukrainian efforts to undermine Trump in the 2016 election.

Menendez asked whether he knew Trump’s personal lawyer, Rudolph W. Giuliani, was “seeking to smear” Yovanovitch.

“I believe he was, yes,” Sullivan said.

But Sullivan said he did not push for a State Department statement of support for her.

Going to the heart of the impeachment inquiry, he was asked whether it was “ever appropriate for the president to use his office to solicit investigations into his domestic political opponents.”

Sullivan said: “I don’t think that would be in accord with our values.”