WASHINGTON — As the special adviser on Europe and Russia for Vice President Mike Pence, Jennifer Williams was one of a handful of national security officials who listened in real time to President Trump’s July 25 telephone call with Volodymyr Zelensky, the president of Ukraine.
Her recollections of that call — based in part on extensive notes she took as the two leaders spoke — have made the veteran Foreign Service officer a key witness in the Democratic-led inquiry into whether Mr. Trump should be impeached for trying to pressure Ukraine to open investigations into his political rivals.
In closed-door testimony last month, Ms. Williams told lawmakers that she was taken aback by Mr. Trump’s insistence during the call that Mr. Zelensky open investigations into former Vice President Joseph R. Biden Jr., a candidate for president in 2020, and his son Hunter Biden, who served on the board of a Ukrainian energy company while his father was in office. She said that the conversation with Mr. Zelensky was “more political in nature” than other calls with foreign leaders that she had listened to and that she felt it was “unusual and inappropriate.”
Ms. Williams noted in particular the mention of “Burisma,” the name of the company that employed Hunter Biden.
The reconstructed transcript of the July 25 call released by the White House did not include the word “Burisma.” But Lt. Col. Alexander S. Vindman, the top Ukraine expert on the National Security Council, also testified that when Mr. Zelensky is shown to have referred to “the company you mentioned,” he actually said “Burisma.” Colonel Vindman said his attempt to correct the record of the call to include the company’s name, and to reflect that Mr. Trump said that he had recordings of Mr. Biden, failed.
On Tuesday, Ms. Williams is scheduled to testify in public, becoming the latest in a series of diplomats to express their concerns about the call.
Over the weekend, Mr. Trump lashed out at Ms. Williams — “whoever that is,” he tweeted — saying that she should read the transcripts of the July 25 call and another one between the two leaders that took place in April. “Then she should meet with the other Never Trumpers, who I don’t know & mostly never even heard of, & work out a better presidential attack!” Mr. Trump wrote. A spokeswoman for Mr. Pence said merely, “Jennifer is a State Department employee.”
A White House official said some were not surprised by Mr. Trump’s attack on Ms. Williams, whom the official described as an innocent bystander in the impeachment mess, and expressed disappointment that senior staff on Mr. Pence’s team did nothing to defend her. The official spoke on condition of anonymity to offer a candid assessment. The person said it reflected poorly on the vice president that he was apparently unable to protect Ms. Williams from being publicly disparaged by the president.
Ms. Williams joined the Foreign Service in 2006 after spending a year as a political appointee working for Michael Chertoff, the secretary of homeland security, in George W. Bush’s administration. In addition to serving in Jamaica under Mr. Bush and in Beirut, Lebanon, under President Barack Obama, Ms. Williams spent about three years working for the State Department on the humanitarian crisis involving refugees in Syria. Six months before Mr. Trump became president, Ms. Williams was transferred to London to work as the deputy spokeswoman at the embassy there.
But in April, she was assigned to Mr. Pence’s staff, becoming one of his top foreign policy advisers even as the campaign intensified by Rudolph W. Giuliani, the president’s personal lawyer, to pressure Ukraine on the investigations that the president wanted.
Democrats are interested in what Mr. Pence knew about the effort to withhold security aid in exchange for a commitment to investigate the Bidens. During the closed-door deposition, Ms. Williams told lawmakers that she was not aware that the vice president was involved in any discussions about the investigations. She said Mr. Pence did not mention investigations to Mr. Zelensky.
But Ms. Williams did shed light on one mystery related to Mr. Pence: why he abruptly canceled his planned trip to Ukraine to attend Mr. Zelensky’s inaugural. Ms. Williams told lawmakers that an assistant to the vice president’s chief of staff, Marc Short, told her in mid-May that Mr. Trump had asked Mr. Pence to stay home.
Ms. Williams said she was never given a reason for the president’s change of mind. The decision not to have Mr. Pence attend the inaugural celebration in late May was cited by the anonymous C.I.A. whistle-blower in the complaint that prompted Speaker Nancy Pelosi to officially begin impeachment proceedings.
Mark Mazzetti contributed reporting.