A foreign affairs adviser to U.S. Vice President Mike Pence — an aide who heard President Donald Trump ask Ukrainian President Volodymyr Zelenskiy to launch an investigation to help him politically — is testifying Thursday before the impeachment inquiry targeting Trump.
Jennifer Williams arrived at the Capitol for a closed-door hearing with impeachment investigators. They are looking to learn how much Pence knew of Trump's efforts to push Ukraine to investigate one of his chief 2020 Democratic presidential rivals, former Vice President Joe Biden, at a time when Trump was temporarily withholding $391 million in U.S. military aid Kyiv wanted.
Williams listened in as Trump on July 25 asked Zelenskiy for "a favor" — the investigation of Biden and his son, Hunter's, work for a Ukrainian natural gas company, and a conspiracy theory that Ukraine meddled in the 2016 U.S. election that Trump won.
In addition, Williams accompanied Pence to a meeting with Zelenskiy in Warsaw on Sept. 1 as the military aid was discussed. Pence aides, however, have said the vice president was unaware that concerns had been raised within the White House and by a whistleblower that Trump had pushed Zelenskiy in the July call for the investigation of the Bidens.
Williams is one of the last witnesses to appear for questioning at a secure room in the Capitol before the Democratic-controlled impeachment inquiry starts public hearings next Wednesday.
Late Wednesday, Trump denied a report that he urged Attorney General William Barr to hold a news conference clearing him of any illegal acts in the July phone call which Trump has repeatedly described as "perfect."
The Washington Post, and later The New York Times, reported that Trump made the request, which Barr declined, around the time the White House released a rough transcript of the call.
The Justice Department issued a statement saying the phone call did not break any campaign finance laws, and "no further action was warranted."
According to the Post, which cited Trump advisers and people familiar with the matter, Trump has in recent weeks said he wished Barr would have held a news conference.
Trump used Twitter late Wednesday to reject the Post's reporting. He described it as "totally untrue and just another FAKE NEWS story with anonymous sources that don't exist."
The Justice Department has not commented. A senior administration official says any report that there is tension between Trump and Barr is "completely false."
A whistleblower's concern about the July phone call led to the current House impeachment inquiry into Trump and whether he withheld military aid to Ukraine unless Zelenskiy publicly committed to investigating Biden for alleged corruption.
Trump has said there was no quid pro quo — military aid in exchange for the Biden investigations.
One of Trump's staunchest defenders, Republican Sen. Lindsey Graham of South Carolina, offered a new defense of Trump on Wednesday, saying, "The Trump policy toward Ukraine was incoherent. It depends on who you talk to. They seem to be incapable of forming a quid pro quo."
House committees on Wednesday released a transcript of last month's testimony by Bill Taylor, the top U.S. diplomat to Ukraine, who told impeachment investigators that it was his "clear understanding" that Ukraine would not get military assistance Trump was withholding unless it launched investigations against Biden and the Democrats.
While Taylor said he had not personally talked with Trump, he testified that the U.S. Ambassador to the European Union, Gordon Sondland, repeatedly told him that while Trump did not see it as a quid pro quo, "I observed that in order to move forward on the security assistance, the Ukrainians were told by Ambassador Sondland that they had to pursue the investigations."
"That was my clear understanding — security assistance money would not come until (Zelenskiy) committed to pursue the investigation," Taylor said.
Taylor is expected to be the Democrats's lead witness when the public hearings open.
The release of Taylor's testimony came as a high-ranking State Department official, David Hale, testified Wednesday about the ouster of America's former ambassador to Ukraine, Marie Yovanovitch, who was viewed by some Trump aides as an impediment to getting Kyiv to open the investigation of the Bidens.
A career diplomat, Yovanovitch was abruptly recalled from Kyiv earlier this year and dismissed from her post months ahead of the scheduled end of her tour.
In the July call with Zelenskiy, Trump described Yovanovitch as "bad news." But State Department officials had told her she had not done anything wrong. Before her dismissal, they had requested she extend her tour into 2020.
Rudy Giuliani, Trump's personal lawyer and delegated by the president to oversee U.S. foreign relations with Ukraine, had pressed for Yovanovitch's ouster and for Ukraine to investigate the Bidens.
While Hale testified, three other Trump administration officials — Energy Secretary Rick Perry, acting White House budget chief Russell Vought and State Department aide Ulrich Brechtbuhl — defied congressional demands that they testify before the impeachment inquiry led by the Intelligence, Foreign Affairs and Oversight committees in the House of Representatives.
Former national security adviser John Bolton, who has said he will not testify without a subpoena, was also expected Thursday to ignore a demand that he appear for questioning.
Trump has been somewhat successful in getting key officials to defy subpoenas in the rapidly expanding impeachment inquiry. But several national security and diplomatic officials, including some still on the government payroll, have told impeachment panels that Trump was at the center of efforts pressing for the Ukraine investigations to help him politically.
Asking a foreign government for help in a U.S. election is against U.S. campaign laws.
But Republican lawmakers defending Trump say the fact that Trump eventually released the military aid to Ukraine proves there was no reciprocal agreement with Kyiv.
WATCH: What does Quid Pro Quo Mean?