Washington (CNN) New revelations about the Ukraine scandal from former national security adviser John Bolton dealt a significant blow to President Donald Trump's defense strategy, contradicting key elements of the case his attorneys presented to senators in his impeachment trial.

According to a bombshell report from The New York Times, Bolton wrote in a draft for his upcoming book that Trump explicitly said he was withholding nearly $400 million in US military assistance until Ukraine helped with investigations into his Democratic rivals. A source with direct knowledge told CNN that the Times' article accurately described the draft manuscript.

Bolton was already considered a key witness to important events in the Ukraine scandal, and Democrats have pleaded with their Republican colleagues to buck the White House and support a subpoena for Bolton. Earlier this month, Bolton even said he'd be willing to testify if he received a subpoena.

The details from Bolton's book create an immediate problem for Trump: They contradict what he and his legal team has been saying, including in arguments on the Senate floor just two days ago when one White House lawyer said there was "no evidence anywhere" of Trump endorsing the quid pro quo.

Here are three ways Bolton's bombshells undermine Trump's case against impeachment.

Quid pro quo confirmed, again

According to The New York Times, Trump told Bolton directly that he didn't want any US aid flowing to Ukraine until Zelensky helped out with the investigations. Trump also used this rationale to rebuff nearly a dozen attempts by Bolton and others to unfreeze the aid package.

That account flies in the face of repeated denials from Trump and his lawyers. Trump has tweeted the phrase "no quid pro quo" more than a dozen times since the inquiry began.

From the beginning, Trump and his allies rejected the notion that he sought a "quid pro quo" with the Ukrainian government. They denied that Trump withheld meetings or foreign aid from Ukraine, and that he didn't pressure Ukrainian President Volodymyr Zelensky to do anything.

"We know there was no quid pro quo on the July 25 call," deputy White House counsel Michael Purpura said Saturday, referring to Trump's call with Zelensky. "We know the Ukrainians did not know that security assistance had been paused at the time of the call. There was simply no evidence anywhere that President Trump ever linked security assistance to any investigations."

In a legal filing last week , Trump's lawyers said, "The evidence squarely refutes the made-up claim that the President leveraged security assistance in exchange for Ukraine announcing an investigation into either interference in the 2016 election or the Biden-Burisma affair."

These arguments were already on shaky ground. That's because multiple witnesses already confirmed the quid pro quo. Gordon Sondland, the Trump-appointed US ambassador to the European Union, directly implicated Trump during his shocking House testimony in November.

Trump pushed back in an overnight Twitter thread . He said, "I NEVER told John Bolton that the aid to Ukraine was tied to investigations into Democrats, including the Bidens," and accused Bolton of trying to pump up book sales.

No policy reason for aid freeze

Bolton's account makes it clear that the reason for freezing US assistance to Ukraine was rooted in Trump's desire for Ukraine to announce the investigations into his political rivals, including former Vice President Joe Biden, a top Democrat vying for his party's nomination this year.

But Trump's lawyers maintained that he imposed the Ukraine freeze for legitimate policy reasons. A five-page section of their trial brief was labeled: "The Administration Paused Security Assistance Based on Policy Concerns and Released It After the Concerns Were Satisfied."

Their brief argued that Trump didn't freeze the aid for political purposes, but because he was genuinely concerned about corruption in Ukraine and wanted to ensure that European nations were also contributing funds. They pointed out that some White House emails, obtained through public records lawsuits, indicate that Trump inquired about burden-sharing early in the process.

This explanation, though, ignored relevant facts that were publicly available even before the Bolton bombshells. For instance, Trump never mentioned the word "corruption" during his July 25 call with Zelensky, and his "anti-corruption" efforts were only focused on one person -- Biden.

Firsthand accounts of Trump

The details of Bolton's manuscript cemented the reality that there are still witnesses who didn't testify to the House but have firsthand knowledge of what happened inside the White House.

The House inquiry was a speedy process, perhaps propelled by Democratic fears that public support for impeachment would slip if they slowed things down and took a more methodical approach. House Democrats invited Bolton to voluntary testify , but they didn't do anything after his lawyer announced he wouldn't appear without a subpoena, and a lengthy court fight loomed.

Without testimony from Bolton or other White House aides, Democrats wrapped up the House inquiry without a smoking gun that Trump explicitly told anybody about the quid pro quo. (House Democrats blamed Trump for these gaps in the evidence, charging him with obstruction of Congress for blocking witnesses and documents.)

Purpura, the White House lawyer, threaded the needle Saturday on the Senate floor, saying: "Not a single witness testified that the President himself said that there was any connection between any investigations and security assistance, a presidential meeting, or anything else."

Trump lawyer Jay Sekulow repeated that carefully worded statement while speaking Monday on the Senate floor.