Witnesses with firsthand knowledge of Trump's pressure campaign against Ukraine blew holes in the GOP's already weak defense.
There were attacks on the credibility of a witness in uniform, and hand-wringing by another witness on all that he knows now that he says he didn't know then. Vice President Mike Pence was name-dropped, and lawmakers heard expressions of concern about the July phone call between President Donald Trump and Ukraine's leader.
The third day of impeachment hearings was the longest yet, bringing to the forefront four witnesses in two separate hearings. All were steeped in national security and foreign affairs.
Some takeaways from Tuesday's testimony:
'Concerned by the call'
Republicans consistently criticize the House impeachment inquiry by saying witnesses didn't have firsthand knowledge of Trump's role in trying to persuade Ukraine to investigate a chief political rival.
On Day 3 of the proceedings, that posture became more difficult to maintain.
The two witnesses in Tuesday morning's hearing each listened to the July 25 phone call in which Trump prodded his Ukrainian counterpart to investigate Democrat Joe Biden.
Jennifer Williams, an adviser to Pence, said she considered the call "unusual" since it "involved discussion of what appeared to be a domestic political matter."
Army Lt. Col. Alexander Vindman, who arrived for the hearing in military uniform adorned with medals, went even further. He considered it "improper," and, acting out of "duty," reported his alarm to a lawyer for the National Security Council.
"My intent was to raise these concerns because they had significant national security implications for our country," Vindman said. "I never thought that I'd be sitting here testifying in front of this committee and the American public about my actions."
For his part, Tim Morrison, who recently left his National Security Council post, said he did not believe that anything illegal occurred on the call but was worried about the political ramifications if the contents leaked.
Attacks on Vindman
Republicans frequently attacked Vindman's credibility, even lacing an occasional nicety with a not-so-veiled barb.
Republican Rep. Chris Stewart called Vindman's uniform a good reminder of his military service but also questioned why Vindman, a Purple Heart recipient, felt it necessary to wear it rather than a suit to the hearing.
He wanted to know, too, if Vindman always insisted on being referred to by military rank rather than "Mr." as he did in an exchange earlier with Rep. Devin Nunes, the committee's top Republican. In that moment, he corrected Nunes and asked to be called "Lt. Col. Vindman, please."
The committee attacks mirrored the combative approach of the White House, which used its official Twitter account to retweet attacks on Vindman, who continues to work at the White House.
Some Republican attacks struggled to land. After Rep. Jim Jordan suggested that Vindman's peers questioned his judgment, Vindman read from a glowing performance review that called him "brilliant" and "unflappable."
Some attacks, including from the White House's director of social media, sought to imply that Vindman, a naturalized American citizen who was a toddler when his family fled Ukraine, may have dual loyalties.
Under questioning from GOP impeachment counsel Steve Castor, Vindman revealed that he was offered three times the post of Ukraine's defense minister while attending Ukrainian President Volodymyr Zelenskiy's inauguration, but "immediately dismissed these offers."
He says two American officials witnessed the exchange with a top adviser to Zelenskiy, and that he notified his chain of command and counterintelligence officials upon returning to the U.S.
Castor questioned whether that created the impression of a conflict, to which Vindman replied, "It's more important what my American chain of command thinks."
There's a lot that Kurt Volker, the former special envoy to Ukraine, contends he didn't know at the time.
He says he didn't know that security aid to Ukraine was linked to the country pursuing investigations.
He says he didn't know that when U.S. officials spoke about investigating Burisma, the Ukraine gas company, that this referred to Biden. He says he should have made that connection much earlier, and had he done so, would have raised objections.
He says he didn't know that then-national security adviser John Bolton had "strong concerns" about discussions of investigations by NSC staff. And he insists that at no time was he aware of an effort to urge Ukraine to investigate Biden, whom he described as an honorable man.
One detail, though, that he recalled on Tuesday that he did not during his closed-door deposition concerned a pivotal July 10 encounter at the White House involving U.S. and Ukrainian officials.
He initially said there was no discussion that day of investigations, but on Tuesday, recalled that Gordon Sondland, the ambassador to the European Union, made a generic comment about them.
Pence has been portrayed largely as out of the loop about Trump's request that Ukraine investigate Biden. Williams' testimony refocused attention on what Pence knew about the events that sparked the House impeachment investigation.
But Pence's office says the vice president and Williams barely interacted.
Williams, a career foreign service officer who was detailed to Pence's office, compiled briefing materials for Pence on Ukraine. She was in the room when he met with Zelenskiy in September and was among the staffers in the White House Situation Room who listened and took notes during the July 25 call.
Katie Waldman, a Pence spokeswoman, noted that Williams' appointment began April 1 and said she "she doesn't directly report to the Vice President."
Pence failed to come to Williams' defense when Trump recently tweeted that she should meet with "the other Never Trumpers, who I don't know & mostly never even heard of, & work out a better presidential attack!"
Williams said she was confused by the attack and "would not" consider herself a "Never Trumper."
White House real-time response
The White House reacted to the impeachment inquiry in real time Tuesday, stepping up its engagement after facing complaints from Republican allies that it wasn't doing enough to fight back.
White House press secretary Stephanie Grisham slammed the first hearing Tuesday as further evidence that Democrats are "blinded by their hatred for Donald Trump and rabid desire to overturn the outcome of a free and fair election."
Trump, at a Cabinet meeting, called the proceedings a "disgrace" and "kangaroo court."
The White House sent a steady stream of "rapid response" emails to reporters beginning before the first witnesses were even sworn-in. The messages sought to defend Trump and undermine the credibility of the witnesses.
"The President of the United States determines American foreign policy – not unelected bureaucrats," said one email, as the White House argued that the career officials testifying had a policy dispute with Trump about Ukraine. "It's the job of bureaucrats to implement that agenda set by the President – not leak and undermine him at every turn."
Trump was criticized by Democrats for his pushback efforts last week, when he tweeted out an attack on former Ambassador to Ukraine Marie Yovanovitch, as she was testifying.