• Cooper said Bolton "was personally involved in many of the events, meetings, and conversations about which you have already received testimony," but also meetings that have yet to be discussed.
  • If he does testify, Bolton could be fatal to President Donald Trump's defense in the impeachment inquiry .
  • Bolton has had more one-on-one interactions with Trump than any other official who's testified so far, and would be the most high-profile witness to testify against the president.
  • According to Axios , Bolton was a prolific note-taker and had a habit of contemporaneously documenting everything that was said in every meeting he participated in.
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Chuck Cooper, the attorney representing former national security adviser John Bolton, dropped an intriguing hint in a letter to Congress last week.

Bolton "was personally involved in many of the events, meetings, and conversations about which you have already received testimony, as well as many relevant meetings and conversations that have not yet been discussed in the testimonies thus far," Cooper wrote.

Cooper was referring to testimony House lawmakers have heard from a slew of government officials and career diplomats in recent weeks as they investigate whether President Donald Trump abused his power by pressuring Ukraine to investigate former Vice President Joe Biden .

The president's allies also conditioned military aid and a White House meeting on Ukrainian President Volodymyr Zelensky acceding to his demands.

The heads of the three House committees leading the impeachment inquiry had asked Bolton to testify behind closed doors, but he failed to show up for his scheduled deposition on Thursday. His lawyer has said Bolton is willing to testify but only if a judge rules that it's ok for him to defy a letter from the White House ordering all administration officials not to comply with the impeachment inquiry.

If he does testify, Bolton could be the most dangerous to Trump so far, especially now, as the impeachment inquiry enters its public phase this week.

As the former national security adviser, Bolton would be the most high-profile official to testify against the president to date.

According to media reports and congressional testimony, Bolton was infuriated by the involvement that Rudy Giuliani, Trump's personal lawyer, and Gordon Sondland, the US's ambassador to the EU, had in conducting what's been described as a shadow foreign policy campaign in Ukraine.

Fiona Hill, the White House's former senior director for Russian and Eurasian affairs, testified to lawmakers that Bolton described Giuliani as a "hand grenade" that would "blow everyone up."

Bolton was also a key participant in a July 10 White House meeting during which Sondland emphasized to Ukrainian officials that they should deliver Trump the investigations he wanted.

Hill testified that when Sondland broached that topic, Bolton abruptly cut the meeting short and immediately told Hill to inform John Eisenberg, the top lawyer on the National Security Council (NSC) of what had transpired. He also told Hill to convey to Eisenberg that he wasn't part of the "drug deal" that Sondland and other Trump allies were "cooking up" in Ukraine.

Cooper's letter to the House general counsel indicates that there may be even more to the story than what's already in the public sphere.

And in Bolton's case, according to Axios , there are receipts.

Current and former senior administration officials told the news outlet that people in Trump's orbit are terrified of what Bolton may have documented and what he might divulge. According to Axios, Bolton is a prolific note-taker and likely has more details than any witness in the impeachment inquiry so far about Trump's shadow campaign in Ukraine.

"Bolton was a voracious note-taker, in every meeting," one source who attended several meetings with the former national security adviser told Axios. Apparently, while others sat and listened in meetings with the president, Bolton "distinguished himself by filling legal pads with contemporaneous notes on what was said in the room."

Trump has a well-documented history of aversion to people recording his statements and actions. Don McGahn, the former White House counsel, told the former special counsel Robert Mueller that the president often grew irritated when he discovered McGahn writing down what was said in their meetings.

"Lawyers don't take notes," McGahn recalled Trump saying after one meeting. "I never had a lawyer who took notes."

McGahn replied that he took notes because he was a "real lawyer" and that notes created a written record and were not a bad thing.

Trump then said he'd "had a lot of great lawyers, like Roy Cohn," McGahn testified. "He did not take notes."

McGahn ultimately proved to be the most harmful witness against Trump in Mueller's obstruction case.

Now, Bolton could step into those shoes as congressional lawmakers investigate whether they should trigger a process that could ultimately result in Trump's removal from office.

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