Kurt Volker, the former special representative for Ukraine negotiations, will dispute Rudy Giuliani’s account of back channel meetings with Ukrainian President Volodymyr Zelensky, sources told the Washington Examiner.

“He's not going to take a fall needlessly for people if it's not warranted,” said Evelyn Farkas, a friend who worked as deputy assistant secretary of defense for three years under Barack Obama.

Volker, 54, who resigned his post as the U.S. special representative for Ukraine last week, will testify Thursday in a deposition that congressional Democrats scheduled as the first major step in an “an expeditious, coordinated” investigation to impeach President Trump. Volker, who took the unpaid diplomatic assignment in addition to his work at the McCain Institute for International Leadership, is expected to prioritize defending his own reputation in a controversy that threatens to consume the administration.

Volker resigned amid a deepening controversy over Giuliani’s efforts to find evidence implicating former Vice President Joe Biden, a perceived front-runner in the 2016 Democratic presidential primaries, in a Ukrainian corruption scandal. In the whistleblower complaint that sparked the inquiry, Volker was portrayed as advising Ukrainian officials on “how to ‘navigate’ the demands” that Trump made during a July 25 phone call in which the president asked the Ukrainian leader to open an investigation into Biden.

“It's fair to say [Volker] resigned his position as envoy so he could assure that he could defend himself and cooperate with the committee,” said Frances Fragos Townsend, a trustee at the McCain Institute, where Volker works as executive director.

Farkas said, "He likely got involved in something sort of inadvertently, meaning he was asked to do one thing and it may have become bigger. But, he certainly would never have condoned anything that would subvert American democracy, or Ukrainian democracy, for that matter."

Giuliani, the president’s personal attorney, maintains that Volker orchestrated his outreach to Zelensky’s team. “He should step forward and explain what he did,” Giuliani said in a television interview last week. “I got a call from Volker. Volker said, ‘Would you meet with him? It would be helpful to us. We really want you to do it.’”

Lawmakers await the explanation slated for Thursday.

"I believe that Kurt will take the position that he was not directing Rudy,” said Townsend. “If anything, Rudy was asking for his assistance and Kurt was not fully aware of what [Giuliani wanted] from the Ukrainians."

That forecast suggests that Volker, who rose through the ranks of the foreign service to be U.S. ambassador to NATO in 2008, will not sacrifice his reputation and future prospects in order to protect Trump.

“If he doesn't cooperate with Congress, he certainly would have a much more difficult time assuming, in the future, a Senate-confirmed position, for obvious reasons,” Farkas said. “I think that may be a motivation, which is fine, and there may be other motivations, so let's let him speak for himself.”

Volker might not be able to convince lawmakers of his ignorance, given that he has made public statements acknowledging that some Ukrainian officials were trying to curry favor with Trump by working with Giuliani.

Farkas believes that Volker aimed to "block Giuliani from doing damage to the United States or Ukraine.”

“I think he's acknowledging that on some level, he knew what was going on, and he was trying to prevent it from getting out of control,” Farkas said, adding that she hadn’t spoken directly on the subject to Volker.

Friends and colleagues in both parties hope Volker can prove that he put Giuliani in contact with Zelensky’s advisers in order to shut down the effort to investigate Biden by allowing the Ukrainian leader’s team to “set him straight.”

“That would be the good news story for Kurt coming out of all of this. Or another possibility that it ends up being that he was playing more of a compromised role,” another foreign policy expert who knows Volker told the Washington Examiner on condition of anonymity. “I certainly hope it's the former, not the latter.”