As President Donald Trump faces the gravest threat to his presidency, one man is at the center of the scandal: his personal lawyer Rudy Giuliani.
The former New York mayor has emerged as the point man in Trump's bid to seek dirt from Ukraine on his potential 2020 Democratic opponent Joe Biden.
That effort to undermine a political rival with the aid of a foreign power led the Democratic-led House of Representatives to launch an impeachment inquiry this week, accusing Trump of abuse of power.
Mr Giuliani, who earned a national profile as mayor of New York City during 9/11, has been a long-time Trump supporter and is one of his most trusted advisers.
"Rudy Giuliani is a great lawyer, he was a great mayor, he's highly respected," Mr Trump said Wednesday.
Mr Giuliani was a surrogate for Mr Trump during the 2016 presidential campaign, delivering a prime-time speech during the Republican convention and making frequent appearances on television.
The attorney's combative TV interviews are legendary, as he spits out sentences rapid-fire, contradicts himself regularly and jumps frenetically from subject to subject.
One such exchange occurred this week when Mr Giuliani was asked in an interview with CNN whether he had asked Ukraine to investigate Mr Biden.
He vehemently denied it but then seconds later said, "Of course I did!"
Any doubts were put to rest with the Wednesday release of the transcript of Trump's July 25 phone call with Ukrainian President Volodymyr Zelensky, during which the president clearly asks the Ukrainian leader to cooperate with mr Giuliani in a probe of the Bidens.
Mr Giuliani and Mr Trump have claimed that Mr Biden, while serving as Obama's vice president in 2016, pressured Ukraine to fire the country's top prosecutor to protect his son, Hunter Biden, who was a member of the board of a gas company in Ukraine accused of corrupt practices.
Those allegations have largely been debunked and there has been no evidence of illegal conduct or wrongdoing in Ukraine by the Bidens.
In the conversation with the Ukrainian president, Mr Trump referred to Mr Giuliani as a "highly respected man" and said he wanted Mr Zelensky to take a call from him to "look into" the Bidens.
"Rudy very much knows what's happening and he is a very capable guy," Mr Trump said. "If you could speak to him that would be great."
The impropriety of such a request notwithstanding, the involvement of Mr Giuliani in foreign affairs has raised eyebrows in Washington.
"What role does Rudolph Giuliani have in this government?" Hakeem Jeffries, a Democratic congressman from New York, asked on Wednesday.
"Is he in the Department of Justice?" Mr Jeffries asked. "Is he the Secretary of State? Is he an ambassador to Ukraine or the European Union?
"Rudolph Giuliani is the president's political hitman," he said.
Mr Giuliani has claimed he coordinated his efforts on Ukraine with the State Department every step of the way.
"I never talked to a Ukrainian official until the State Department called me and asked me to do it," Mr Giuliani told Fox News. "And then I reported every conversation back to them."
The Washington Post quoted former and current US officials, however, as voicing displeasure with Mr Giuliani's forays into the diplomatic arena.
"We had the same visibility as anybody else -- watching Giuliani on television," a former senior official told the newspaper.
A current US official placed the blame for the Ukraine scandal squarely at Giuliani's feet.
"Rudy -- he did all this," the official told the Post, blaming the crisis on Giuliani "injecting himself into the process."
In his call with Mr Zelensky, Mr Trump asked the Ukrainian president to cooperate not only with Mr Giuliani in a probe of Mr Biden but also with Attorney General Bill Barr.
The Justice Department said Wednesday that Mr Barr had not "discussed this matter, or anything relating to Ukraine, with Rudy Giuliani."
After being passed over for a position in the Trump cabinet, Mr Giuliani served as the president's adviser for cybersecurity before becoming his personal lawyer in April 2018.
He notably helped lead Mr Trump's defense during the investigation by Special Counsel Robert Mueller into whether his 2016 presidential campaign had colluded with Russia to win the White House.
Mr Trump said on Wednesday that Mr Giuliani's involvement with Ukraine was an attempt to discover how the "phony witch hunt" started -- the president's standard dismissive reference to the Mueller probe.
"Rudy's got every right to go and find out where that started and other people are looking at that too," Mr Trump said.