Inside President Donald Trump's push for Ukraine probe of Democratic rival

When Rudy Giuliani, the president's personal attorney, endeavored in early 2019 to have former Vice President Joe Biden investigated in Ukraine, one of his points of contact was the country's former prosecutor general, Viktor Shokin, whose ouster in March of 2016 -- and Biden's involvement in it -- has become the subject of controversy.

During an appearance on CNN Thursday night, Giuliani said "of course" he asked the Ukrainians to investigate Biden, before backtracking.

"I didn't ask them to look into Joe Biden," Giuliani said. "I asked them to look into the allegations that related to my client, which tangentially involved Joe Biden in a massive bribery scheme."

The "bribery scheme" Giuliani has accused Biden of dates back to 2014, when the then-vice president led the Obama administration's efforts to root out corruption in Kiev in the wake of the Ukrainian revolution. As part of his efforts, Biden called for the dismissal of Shokin, who had ostensibly been leading a probe into Burisma, an oil company that had recently added the president's son, Hunter Biden, to its board of directors.

On Friday, The Wall Street Journal reported that President Donald Trump had pressured Ukrainian President Volodymyr Zelensky, about eight times, to work with Giuliani to investigate Biden. In response, the Biden campaign called on the president to release a transcript of the call "so that the American people can judge for themselves."

"If these reports are true," Biden said in that statement, "then there is truly no bottom to President Trump's willingness to abuse his power and abase our country. This behavior is particularly abhorrent because it exploits the foreign policy of our country and undermines our national security for political purposes.

"It means that he used the power and resources of the United States to pressure a sovereign nation -- a partner that is still under direct assault from Russia -- pushing Ukraine to subvert the rule of law in the express hope of extracting a political favor."

In an interview with ABC News in May of 2019, Shokin, the former prosecutor, suggested that the then-vice president sought his dismissal as part of an effort to protect his son and the company for which he worked.

"Biden was acting not like a U.S. vice president, but as an individual," Shokin told ABC News, "like the individual interested in having me removed -- having me gone so that I did not interfere in the Burisma investigation."

The assertion that Biden acted to help his son has been undercut by widespread criticism of Shokin from several high-profile international leaders who said Biden's recommendation was well justified.

A Biden campaign spokesman rejected the premise of Shokin's allegation, saying Biden had "acted at all times in a manner consistent with well-established executive branch ethics standards."

Regardless, Shokin and Giuliani connected in 2019. The two spoke only once, via Skype, according to Shokin. The bulk of their conversation focused on an issue Shokin had with his visa application to visit the U.S., but he conceded that Biden's name was mentioned -- though he was unsure by whom.

Shokin insisted Giuliani did not attempt to "dig up dirt on Joe Biden" and scoffed when pressed repeatedly about whether his interaction with Giuliani about Biden constituted election meddling, denying it out of hand.

"The thing is that I am not a politician," Shokin said, "and for me to give a political assessment of some actions is very difficult."

Daria Kaleniuk, a Ukrainian anti-corruption advocate, perceived Shokin's relationship with Giuliani in a different light, regardless of Shokin's insistence.

"[Giuliani] is a private lawyer, private attorney of President Trump, and I think what he is doing actually is very risky for relationships between Ukraine and between the United States," Kaleniuk said. "I don't want my country to be used as a political football."

Giuliani's overtures to Ukrainian officials has come under renewed attention as a result of a mysterious whistleblower complaint surrounding the president's conduct during a phone call regarding Ukraine.

On Friday, Trump told reporters that "there was nothing said wrong" during a July of 2019 phone conversation with Zelensky and accused the whistleblower on Twitter of being "highly partisan."

While details of the call remain unclear, a Ukrainian readout of the conversation cited a discussion about "investigations into corruption cases that have hampered interaction between Ukraine and the U.S.A."

In the Oval Office on Friday, Trump declined to say whether he brought Biden up during his phone call with Zelensky.