The whistleblower complaint at the center of Washington's political firestorm not only sparked a call for an impeachment investigation, but also has put President Donald Trump's allies on the defensive.
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As the White House pushes back against the House Democrats' impeachment proceedings, Trump and his defenders have tried to shift the focus back to the original whistleblower, Vice President Joe Biden and his son, Hunter Biden, repeatedly making accusations of fraud and misconduct and questioning motives.
Here is a look at of some of their most significant accusations:
Accusation: The whistleblower is driven by politics
In a tweet earlier this week, Trump referred to the whistleblower as "highly partisan" with ties to his political rivals. But those statements aren't supported by the facts known so far, and lack important context.
Trump told reporters on Wednesday at the White House that "it turns out that the whistleblower is a Democrat."
The whistleblower's identity hasn't been revealed but the person has previously been identified as an intelligence official, a career civil servant and a registered Democrat.
According to the intelligence community inspector general, the person was screened for any potential bias during an interview after filing the complaint and showed "some indicia of an arguable political bias." Despite that, the IG said he found that the whistleblower's allegations appeared "credible."
In a statement, the whistleblower's lawyers say the person has never worked for any political candidate, campaign or party and "spent their entire government career in apolitical, civil servant positions in the Executive Branch."
As a career civil servant, it's very possible the person served under then-Vice President Joe Biden or provided briefings on Capitol Hill to lawmakers, but such a role would not normally be considered political.
Accusation: The whistleblower got facts wrong on Trump's call with Zelenskiy
Trump tweeted that, "the first so-called second-hand information ‘Whistleblower' got my phone conversation almost completely wrong."
But so far, most of the allegations have been substantiated by other evidence, most notably a rough transcript of Trump's phone call released by the White House. In that transcript, Trump asks Ukrainian President Volodymyr Zelenskiy for a "favor" and asking him to investigate Joe Biden and his son.
Private text messages exchanged by top U.S. diplomats also show at least two believed Trump wanted Ukraine to launch an investigation, and that he wanted to dangle a meeting between the two leaders in return. At least one diplomat was deeply concerned by the possibility that Trump was holding up military aid in exchange for the investigation.
One detail in the whistleblower's complaint has been disputed: that T. Ulrich Brechbuhl, a State Department official, was listening to the July 25 Trump-Zelenskiy conversation. The State Department has said he was not on the phone call.
Accusation: The whistleblower has only second-hand information
In the complaint, the whistleblower said the information came from more than a half dozen White House and U.S. officials and acknowledges that he "was not a direct witness to most of the events described."
But the intelligence community inspector general later noted that the whistleblower had "direct knowledge of certain alleged conduct."
Mark Zaid, an attorney representing the whistleblower, says he is now representing a second intelligence official with first-hand knowledge of some of the allegations outlined in the original complaint.
Trump and his defenders also have claimed that whistleblower process was changed right before this complaint to allow one to be based on second-hand information, but the inspector general put out an unusual public statement saying that accusation was unfounded.
Accusation: Joe Biden wanted a Ukrainian prosecutor fired to protect his son, Hunter Biden
In a September tweet, Trump wrote that Biden demanded "the Ukrainian Government fire a prosecutor who was investigating his son, or they won't get a very large amount of U.S. money."
This accusation is misleading, as there was widespread and global criticism of the Ukrainian prosecutor general at the time. In other words, there were grounds for Biden to urge his dismissal that had nothing to do with his son. Several high-profile Western leaders have said Biden's recommendation was prudent.
The International Monetary Fund, for example, threatened to withhold aid to Kiev in early 2016, while the former prosecutor was still in office, citing "Ukraine's slow progress in improving governance and fighting corruption," according to Christine Lagarde, then the IMF's managing director.
Accusation: Hunter Biden earned thousands as a member of Burisma's board
Hunter Biden and an associate at a business entity called Rosemont Seneca Partners both obtained seats on the board of the Ukrainian energy company at about the same time.
According to banking records reviewed by ABC News, their firm began collecting $166,666 payments each month from Burisma, owned by a Russian oligarch.
Accusation: Hunter Biden had no relevant experience that qualified him for a board position at Burisma
It is true that he had no significant prior experience in the energy industry or Eastern Europe, where Burisma operated. In a statement to ABC News in June, Hunter Biden defended his "qualifications for such a role based on [his] extensive prior board service," including "as former Chairman of the Board of Directors of World Food Program USA" and "serving as former Vice Chair of the Board of Directors of the National Railroad Passenger Corporation (Amtrak)."
Accusation: Hunter Biden pocketed $1.5 billion from an investment firm deal in China
Reports at the time indicated Hunter Biden's firm, Bohai Harvest RST, sought to raise $1.5 billion from a deal involving a Chinese-state-run bank. This does not mean that either he or his firm pocketed $1.5 billion from the deal.
Trump in two separate tweets said that Hunter Biden"…got 1.5 Billion Dollars from China despite no experience and for no apparent reason."
A lawyer for Hunter Biden, George Mesires, told ABC News the fund has a registered capital of $4.2 million, and Hunter Biden holds a 10% stake. The lawyer estimated that committed capital is worth $420,000.
Mesires also said Hunter Biden has yet to receive a financial return on investment, adding that he only became a minority stake-holder in the company in October 2017 – after Joe Biden was no longer vice president. Prior to then, Hunter Biden served as an unpaid director.
It was not immediately clear whether he invested that money himself or whether his 10% stake serves as compensation for his directorship.
Accusation: Hunter Biden scored the deal right after he flew to Beijing with his father on Air Force Two
It's true that at the time of his visit to Beijing in late 2013, Hunter Biden was engaged in business there as a participant in a company called Bohai Harvest RST.
Hunter Biden told The New Yorker he went on the visit with his teenage daughter, who was accompanying Vice President Joe Biden and flew on Air Force Two – the vice president's plane. He acknowledged he also met with some business associates in a social capacity during that trip.
Hunter Biden's lawyer said the agreement actually was signed months earlier, in June. A Chinese business license was issued shortly after his visit to Beijing in December 2013.
Accusation: The US ambassador to Ukraine was ‘bad news'
In the July 25 conversation, Trump called her "bad news," a former Ukrainian official alleged she gave him a "do-not-prosecute" list and Trump's personal lawyer, Rudy Giuliani, has alleged she had an anti-Trump bias. And he told reporters publicly in early October that he had "heard very, very bad things about her for a long period of time."
But the accusations against Ambassador Marie Yovanovitch haven't lined up.
The State Department at the time said the allegation that she asked the Ukraine government not to prosecute certain people was an "outright fabrication" and "does not correspond to reality." Yovanovitch had been trying to tackle corruption and had criticized the Ukraine official who made the unsubstantiated claim.
On Thursday, the indictment charging two Giuliani associates with campaign finance violations revealed that the duo attempted to get a member of Congress to help oust Yovanovitch as ambassador "at the request of one or more Ukrainian government officials."
Retired ambassador Nancy McEldowney described Yovanovitch as a "professional of impeccable integrity, someone with a stellar career that has never had the slightest suggestion of impropriety."