Democrats have loathed John Bolton for years. Now, he could be their star witness against Trump.

• Democrats have long loathed former national security adviser John Bolton, but he could be their most dangerous witness against President Donald Trump in Congress' impeachment inquiry.
• Bolton attended a July 10 White House meeting with Ukrainian officials during which one of Trump's allies explicitly raised the subject of a quid pro quo with Ukraine.
• He was staunchly opposed to Trump's infamous July 25 phone call with Ukraine's president because he feared Trump would use it to air his personal grievances and push for politically motivated investigations.
• Bolton's lawyer dropped a tantalizing hint in a letter to Congress earlier this month indicating that Bolton knows even more than what's already been revealed.
• Most importantly, Bolton has receipts. He's a prolific note-taker and his documents could prove devastating to a White House swimming through a mountain of evidence Democrats have collected.
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For Democrats, it couldn't get worse than John Bolton.

In 2018, he became the latest national security adviser to come through the revolving door of the Trump administration, which has seen more turnover than any other administration in recent history.

Bolton is famously hawkish and a key architect of the disastrous Iraq War. Before his ouster in September was seen by Democrats as a warmonger who would pull the country into military conflict in any number of regions - not the least of which were Iran, North Korea, and Venezuela.

Now, he could be the star witness in the House of Representatives' impeachment proceedings against President Donald Trump.

At the center of the inquiry are Trump's efforts to strongarm Ukraine into delivering political dirt on former Vice President Joe Biden and the 2016 election while withholding vital military aid and a White House meeting that Ukrainian President Volodymyr Zelensky desperately sought.

The whistleblower complaint that sparked the inquiry described Trump's behavior as an abuse of power and added that the president tried to use his public office for private gain by soliciting foreign interference in the 2020 election.

Congress and the public have already heard testimony from over a dozen witnesses who appeared after being subpoenaed, and often in direct defiance of the White House's orders. But all the while, Bolton - who has so far refused to testify - has loomed large over the proceedings.

The former national security adviser is currently waiting for a judge to weigh in on whether he has to abide by the White House's directive not to testify or if he must comply with a congressional subpoena. The public can expect a ruling on the matter on December 10.

Democrats have signaled they may not even call Bolton to testify because they already have enough evidence to begin drafting articles of impeachment against the president. But if the court allows Bolton to testify, he could be instrumental in helping Democrats cement their case.

Bolton was front and center in key events that led to the impeachment inquiry

• Bolton is at the center of several key events being scrutinized as part of the impeachment inquiry. As the former national security adviser, he would be the most high profile witness to testify against the president.
• He attended a July 10 meeting at a White House policy meeting between senior US and Ukrainian officials. Gordon Sondland, the US's ambassador to the EU, hijacked the meeting when he told the Ukrainians that Trump wanted a "deliverable" - specifically, politically motivated investigations - in exchange for a White House meeting.
  • Bolton immediately cut the meeting short at that point and informed Fiona Hill, who at the time was the National Security Council's senior director in charge of Russian and Eurasian affairs, to "tell the lawyers" what had happened.
  • According to Hill's testimony, Bolton ordered her to tell John Eisenberg, the NSC's chief counsel, that he was not part of "whatever drug deal" Sondland and Mick Mulvaney, the acting White House chief of staff, were "cooking up in Ukraine."
• Bolton was staunchly opposed to Trump making the infamous July 25 phone call to Zelensky.
  • Hill and other witnesses have testified that Bolton was against the phone call because he feared the president would use it to air his personal grievances to Zelensky, which is exactly what ended up happening.
  • Lt. Col. Alexander Vindman, the NSC's top Ukraine expert, prepared a list of talking points for Trump before the phone call. The list touched on key US policy issues with respect to Ukraine.
  • But Vindman testified - and a White House summary showed - that Trump didn't bring up any of those points and instead used the conversation to pressure Zelensky to investigate the Bidens, Burisma Holdings, and a bogus conspiracy theory about Ukrainian interference in the 2016 election.

Bolton could be Rudy Giuliani's worst nightmare

• The former national security adviser described Rudy Giuliani, Trump's personal lawyer who's spearheaded what witnesses have said was the "irregular channel" of foreign policy in Ukraine, as a "hand grenade." He was also opposed to the smear campaign Giuliani and Trump carried out against Marie Yovanovitch, who at the time was the US's ambassador to Ukraine.
  • Hill testified to Congress that Bolton was aghast at Giuliani's multitude of television appearances, in which he pushed conspiracies about Yovanovitch, the Bidens, and the 2016 election.
  • "We saw him often on television making these statements," Hill said of Giuliani. "And I had already brought to Ambassador Bolton's attention the attacks, the smear campaign, against Ambassador Yovanovitch and expressed great regret about how this was unfolding, and in fact, the shameful way in which Ambassador Yovanovitch was being smeared and attacked."
  • Hill said that when she asked Bolton if they could intervene, he "looked pained, and basically indicated with body language that there was nothing much we could do about it."
  • "And he then, in the course of that discussion, said that Rudy Giuliani was a hand grenade that was going to blow everyone up," Hill testified.
  • Asked why Bolton described Giuliani that way, Hill told Congress the former New York mayor was "clearly pushing forward" issues that would "probably come back to haunt us. That's where we are today."

Bolton has receipts

• Bolton's lawyer dropped a tantalizing hint in a letter to Congress earlier this month indicating that Bolton knows even more than what's already been revealed.
  • 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," Chuck Cooper, Bolton's attorney, wrote.
• Bolton has receipts.
  • Current and former senior administration officials told Axios 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."

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