Kurt Volker, the former U.S. special envoy to Ukraine, told lawmakers  Tuesday that he should have surmised President Donald Trump’s calls for a Ukrainian probe were actually code for an investigation into former Vice President Joe Biden, a chief political rival. 

During the fourth public impeachment hearing into Trump’s dealings with Ukraine, Volker said he knew that Biden’s son Hunter was once on the board of Ukrainian gas company Burisma but did not think investigations into the company were essentially probes into the Biden family. 

Volker said he later came to understand that Burisma, a Ukrainian gas company, was code for a politically motivated inquiry the Bidens.

“I did not understand that others believed that an investigation of the Ukrainian company Burisma, which had a history of accusations of corruption, was tantamount to investigating Vice President Biden,” Volker said. “I drew a sharp distinction between the two.”

He said that an investigation into Burisma would be “appropriate and unremarkable,” but an investigation into the Bidens would be “unacceptable.”

Volker said that if he had understood key players were conflating investigations of Burisma and the Bidens, he would have responded differently.

“In retrospect, I should have seen that connection differently, and had I done so, I would have raised my own objections,” Volker said.

Volker’s testimony sets him apart from other officials who have testified in the impeachment inquiry that the conflation of the oil company and the politically motivated investigations were clear. Even a text message from U.S. ambassador to Ukraine William B. Taylor submitted to the House Intelligence Committee last month shows that specific concern arising.

A May 26 message from Taylor to Volker says that Taylor was stressed by the decision over whether to return to Kyiv.

“Can anyone hope to succeed with the Giuliani-Biden issue swirling for the next 18 months?” Taylor asked.

When he spoke with Rudy Giuliani, the president’s personal attorney, Volker says he stressed that it was not credible to him that Biden would have been influenced by personal or financial motives from carrying out his duty as vice president.

“The accusation that Vice President Biden acted inappropriately did not seem at all credible to me,” Volker said.

He added that he had known Biden for 24 years, saying “he is an honorable man and I hold him in the highest regard.”

Volker’s testimony Tuesday in open session also offered a key departure from his closed-door testimony on Oct. 3.

In his opening statement before the House Intelligence Committee, Volker said that at the end of a July 10 meeting, Gordon Sondland, the U.S. ambassador to the European Union, “made a generic comment about investigations.” 

“I think all of us thought it was inappropriate; the conversation did not continue and the meeting concluded,” Volker said. Then-National Security Adviser John Bolton and Alex Danylyuk, then the chairman of the Ukrainian National Security and Defense Council, were in the meeting. 

If there was further discussion of investigations or Burisma on July 10, Volker said it’s possible they occurred while he was engaged in a side conversation or after he had already left the room.

That’s a change from his closed-door testimony in which he said that investigations were not brought up in the July 10 meeting, an assertion that was contradicted by other officials in the room.

Lt. Col. Alexander Vindman testified Bolton shut down the meeting following Sondland’s investigations comment, a dramatic twist that wasn’t mentioned in Volker’s original or updated public testimony.

Volker instead described that the July 10 meeting had not been a great success because Ukrainian officials gave a boring and bureaucratic presentation that didn’t give the Americans in the room a better understanding of political dynamics at play for Ukrainian President Volodymyr Zelenskiy.

Another contradiction arose in Tuesday’s hearing. Tim Morrison, the former senior NSC director for Europe and Russia policy said he was told it was a “mistake” that the call summary of Trump’s July 25 phone call with Zelenskiy was put on a secure server used for classified information.

Earlier in the day, Vindman said the summary was moved to the secure server “intentionally.”