Former G.O.P. Lawmaker Pressed for Ambassador’s Ouster, Diplomat Will Say

WASHINGTON — Robert Livingston, the former Republican congressman turned lobbyist, repeatedly told a foreign service officer assigned to the White House that the American ambassador to Ukraine should be fired because of her association with Democrats, the officer plans to tell impeachment investigators on Wednesday.

The officer, Catherine M. Croft, will testify that she “documented” multiple calls from Mr. Livingston about the ambassador, Marie L. Yovanovitch, while she was working at the National Security Council from mid-2017 to mid-2018. She plans to say she informed two other officials — Fiona Hill, then the senior director for Europe and Russia at the council, and George P. Kent, a Ukraine expert at the State Department — about them at the time.

“He characterized Ambassador Yovanovitch as an ‘Obama holdover’ and associated with George Soros,” she will say, referring to the billionaire liberal philanthropist, according to a copy of Ms. Croft’s opening statement reviewed by The New York Times. “It was not clear to me at the time — or now — at whose direction or at whose expense Mr. Livingston was seeking the removal of Ambassador Yovanovitch.”

The testimony shifts forward by several months a timeline of known attacks on Ms. Yovanovitch by conservatives questioning, without evidence, her loyalty to President Trump. It is not clear if Mr. Livingston’s work, or those financing it, were in any way connected to efforts by two Americans with business interests in Ukraine who wanted her gone and, later, by Mr. Trump’s private lawyer, Rudolph W. Giuliani. Nor did Ms. Croft have anything to say about who else Mr. Livingston spoke with.

Still, the outreach is certain to interest impeachment investigators, who are scrutinizing smears against Ms. Yovanovitch to understand if they were part of a larger pressure campaign by Mr. Trump and Mr. Giuliani to secure from Ukraine politically beneficial investigations into Democratic rivals. Mr. Trump eventually recalled her this spring from Kiev, months ahead of schedule.

Ms. Croft is one of two witnesses the House committees leading the inquiry will summon on Wednesday. Both served as advisers to Kurt D. Volker, the United States’ special envoy to Ukraine, and in other diplomatic capacities related to that country. The other is Christopher J. Anderson, who preceded Ms. Croft as Mr. Volker’s adviser.

Investigators will be keen to press both officers to confirm aspects of testimony given earlier by Mr. Volker and fill in details about his work trying to manage the demands of Mr. Trump and Mr. Giuliani on the new Ukrainian president, Volodymyr Zelensky. They are expected to testify despite State Department orders not to.

Mr. Volker told investigators that he had not been aware of any quid pro quo demanded by Mr. Trump, but he detailed how Mr. Giuliani pressed the Ukrainians to publicly pledge that they would undergo investigations that could damage the president’s political domestic adversaries. And text messages he shared with Congress at least appeared to show that a coveted White House meeting for Mr. Zelensky would come only if they agreed to certain investigations.

According to a copy of his own opening statement, Mr. Anderson will testify that he and Mr. Volker worked to accommodate Mr. Giuliani’s influence as they tried to help Ukraine’s new government root out corruption in general and deepen its ties to the United States — but bumped up against it again and again.

Mr. Anderson plans to describe a June 13 meeting at the White House with Mr. Volker and John R. Bolton, then Mr. Trump’s national security adviser, in which Mr. Bolton indicated that Mr. Giuliani could pose a problem as they sought to build more support for Mr. Zelensky among senior White House officials.

“He cautioned that Mr. Giuliani was a key voice with the President on Ukraine which could be an obstacle to increased White House engagement,” Mr. Anderson planned to say. He will add that he wrote a summary of Mr. Bolton’s remarks about Mr. Giuliani and shared it with Mr. Kent and others at the State Department.

Other witnesses have testified that Mr. Bolton expressed alarm at Mr. Giuliani’s role in even more vivid terms on other occasions.

During another meeting of senior officials at the Energy Department a few days later, Mr. Anderson plans to testify, there were “vague discussions in the meeting about how to address Mr. Giuliani’s continued calls for a corruption investigation.”

Ms. Croft, who took over as Mr. Volker’s adviser in July, appears to have less to say about Mr. Giuliani.

As for Mr. Livingston, Ms. Croft does not precisely date the outreach in her opening statement, but she was assigned to the National Security Council as Ukraine director from July 2017 to July 2018, when she left for another government posting.

In her own testimony before impeachment investigators, Ms. Yovanovitch said that she was informed upon removal that Mr. Trump had lost faith in her and had been seeking her ouster since summer 2018. Ms. Yovanovitch, a career diplomat and veteran ambassador, said that she had no bias against Mr. Trump and that her bosses at the State Department had acknowledged she did “nothing wrong.”

Mr. Livingston was once a household name in Washington, and closely associated with the impeachment of another president, Bill Clinton. In 1998, Mr. Livingston was on the cusp of being elected House speaker as Republicans were preparing to impeach Mr. Clinton, but he abruptly resigned after details of his extramarital affair became public.

Foreign Agents Registration Act filings show that Mr. Livingston’s firm, the Livingston Group, has represented Ukrainian clients in the past, including in 2018.

Ms. Croft may also have other information of interest to investigators, including about Mr. Trump’s dealings with Mr. Zelensky’s predecessor. She plans to say that during her time at the National Security Council, she staffed a September 2017 meeting between Mr. Trump and President Petro O. Poroshenko of Ukraine and was involved that winter in Mr. Trump’s decision to sell Javelin missiles to Ukraine.

As part of their work, House Democrats are investigating whether Mr. Trump later tried to use $391 million in military aid as leverage to secure the investigations he wanted into former Vice President Joseph R. Biden Jr. and an unproven theory about Democrats colluding with Ukraine in the 2016 election. Ms. Croft will say she learned that Mr. Trump had frozen the aid in July.

Both Ms. Croft and Mr. Anderson intend to warn about the risks of a failure by the White House to support Mr. Zelensky and Ukraine in their continuing military conflict with Russia.

“His best chance at success is with our support along with our European partners,” Ms. Croft will say. “It is my hope that even as this committee’s process plays out, we do not lose sight of what is happening in Ukraine and its great promise as a prosperous and democratic member of the European community.”

In one case, Mr. Anderson plans to say, the senior White House officials blocked the release of a statement prepared by the State Department that would have condemned Russia for attacking and seizing Ukrainian military vessels in November 2018. Mr. Volker ended up sending his own tweet.

Mark J. MacDougall, a lawyer for both witnesses, planned to tell investigators for the House Intelligence, Foreign Affairs, and Oversight and Reform Committees that neither Ms. Croft nor Mr. Anderson is the anonymous whistle-blower whose complaint about Mr. Trump’s actions toward Ukraine helped prompt the impeachment inquiry. But in a statement of his own, he will say that neither witness would be willing to answer questions they believe may be meant to identify the whistle-blower.

“To the extent we reasonably conclude that any questions directed to Mr. Anderson this afternoon are intended to assist anyone in establishing the identity of the whistle-blower, we will make the necessary objections and will give the witness appropriate instructions,” Mr. MacDougall planned to say.

His decision to offer such introductory remarks was unusual, and reflected the extent to which accounts of Republican questioning related to the activity of the whistle-blower has spooked potential witnesses.

Sharon LaFraniere contributed reporting.