As an Army officer who worked on Ukraine policy on the White House told the House of Representatives’ impeachment inquiry that President Trump’s pressure on Ukraine to investigate domestic adversaries was “inappropriate,” congressional Republicans suggested that he was insufficiently loyal to the United States.

The attack, previewed for weeks in conservative media, came from Republican counsel Stephen Castor. Castor asked if a former aide to Ukrainian President Volodomyr Zelensky, Oleksandr Danyluk, ever offered the job of Ukrainian defense minister to Lt. Colonel Alexander Vindman, a decorated infantry officer and veteran of the Iraq war who came to the U.S. as a child refugee from the Soviet Union.

“I’m an American,” said Vindman, who testified on Tuesday in his dress uniform. “I came here as a toddler and immediately dismissed these offers.”

The brazen attack on Vindman underscored the stakes of his testimony and the damage it could do to Trump, who denies all wrongdoing.

Trump’s congressional allies dismissed testimony last week from three senior U.S. diplomats on grounds that they lacked direct knowledge of administration Ukraine policy in the pivotal summer of 2019. But Vindman was on the fateful July 25 phone call between Trump and Ukrainian President Volodomyr Zelensky in which Trump asked for “a favor” in the form of investigations of the Bidens. Even prime Trump ally Devin Nunes (R-CA), the intelligence committee’s ranking Republican, said Vindman had the “first-hand” knowledge that prior witnesses lacked.

And also unlike those witnesses, Vindman was willing to characterize the president’s behavior not as “irregular” but wrong.

“It was inappropriate, it was improper for the president to demand an investigation into a political opponent, especially a foreign power where there’s at best dubious belief that this would be a politically impartial investigation,” Vindman told the House intelligence committee. He testified alongside his counterpart on Vice President Mike Pence’s staff, Jennifer Williams.

Vindman testified that the “power dynamics” behind Ukrainian dependence on the U.S. for weapons against Russia meant that Trump was “demand[ing]” Zelensky commit to investigating Trump’s rivals. It undercut Trump’s defenders’ insistence that Trump was not putting any pressure on Ukraine by withholding $400 million of security assistance and a still-never-manifested White House meeting.

After the exchange with Castor, Democrats on the Intelligence panel held up the GOP’s focus on the outlandish defense-ministry offer as Exhibit A of what they describe as a smear. Rep. Jim Himes (D-CT) was particularly fired up, saying Castor’s approach came cloaked in “a Brooks Brothers suit and parliamentary language” but only served to give right-wing media “an opening to question [Vindman’s] loyalty.”

"It's the kind of thing you say,” said Himes, “when you're defending the indefensible."

Rep. Sean Maloney (D-NY) later referred to the insinuation as “an old smear we’ve heard many times in our history, and Rep. Raja Krishnamoorthi (D-IL), an immigrant himself, told Vindman “it appears your immigrant heritage is being used against you.”

Oleksandr Danyluk, a former national-security aide to Zelensky, told The Daily Beast that the supposed offer was “clearly a joke.”

Danyluk, who said he only remembers speaking with Vindman once about the defense minister position - rather than the three times Vindman recalls, said it occurred during a light-hearted exchange about how the two used to live close to one another in the former Soviet Union. He then joked he should become the defense minister.

“We both smiled and laughed,” Danylyuk said.

Republicans seemed to shrug off the questioning. After the hearing ended, Rep Jim Jordan (R-OH) told reporters that Vindman “didn’t seem too troubled” by what Castor had asked.

“I think it’s just a perception issue,” said Jordan, who added he couldn’t understand why Democrats were talking about the dual loyalty charge. “That’s ridiculous. Steve Castor did an amazing job today.”

But Castor’s line of questioning followed a series of dual-loyalty attacks and general attacks on Vindman by Trump and his allies. “I don’t know that he’s concerned about American policy,” former Rep. Sean Duffy told CNN, while the Bush administration’s torture-approving attorney, John Yoo, baselessly likened Vindman’s alarm at the Ukraine arm-twisting to “espionage.” Trump himself called Vindman a Never Trumper, a term he also hurled at Pence aide Williams. Sen. Ron Johnson (R-WI), who was part of the pressure effort on Ukraine, dismissed Vindman part of a cohort of “bureaucrats” that have never accepted Trump’s legitimacy and said he “fit the profile” of a Trump-sabotaging prolific leaker—even though Vindman said in his deposition that Trump was “my Commander in Chief, I'm not trying to, you know, be overly critical of the president.”

In another exchange on Tuesday, Jordan read from the previous deposition of NSC official Tim Morrison, who replaced Fiona Hill as Vindman’s superior. Morrison told congressional investigators that he, and others, were concerned about Vindman’s judgement and believed he may be speaking to the press.

“Your former boss, Dr. [Fiona] Hill, had concerns about your judgment,” Jordan added. “Your colleagues had concerns about your judgment and your colleagues felt that there were times when you leaked information. Any idea why they have those impressions, Colonel Vindman?”

Vindman, who had clearly anticipated this line of questions, answered by reading a positive performance review Hill had written him before her departure over the summer. It did not stop the White House from tweeting out Morrison’s deposition quote about Vindman.

Early on in the hearing, Republicans also quickly dove right into a hunt for the whistleblower’s identity and details on anyone in the White House who might have leaked information about the Ukraine matter to the press. In the lead-up to the hearing, GOP allies of the president had suggested Vindman in particular was the impeachment witness most connected with the anonymous whistleblower.

Nunes, for example, asked Vindman who else in the government he spoke with about the July 25 call. Vindman said he spoke to an individual in the intelligence community, among others.

“As you know, the intelligence community has 17 different agencies,” said Nunes. “What agency was this individual from?” At that point, House Intelligence Committee Chairman Adam Schiff (D-CA) shut down the fishing expedition: “I want to make sure that there's no effort to out the whistle-blower through these proceedings,” he said.

It was not a new tactic from the GOP: during Vindman’s closed-door deposition, they tried on several occasions to get him to name the whistleblower outright or reveal any details about the person’s identity. Vindman told investigators that he did not know who the person was.

Nunes also asked both Vindman and Williams a series of questions asking if they had spoken to the press directly about Trump and Ukraine or knew who did. Both said they did not. “I do not engage with the press at all,” said Vindman, who certain Republicans suggested—without any hard evidence—is the kind of administration official who leaks to the press.

Vindman has said he was “concerned” by the call, which seemed to him to insert a domestic “partisan play” into bilateral relations. He has testified said the version of the call that the White House released in September omitted material information, such as a direct reference from Zelensky to Burisma, the natural gas company that gave Joe Biden’s son a seat on its board – which Vindman said “suggested he had been prepped.”

Vindman was also present two weeks earlier for a meeting with a senior Zelensky national-security aide whom U.S. Amb. to the European Union Gordon Sondland pressured to open an investigation into the Bidens as a prerequisite for Zelensky visiting the White House. That July 10 meeting, Vindman had already told the inquiry in his deposition, prompted immediate objections from his boss, then-senior NSC director Fiona Hill, and her boss, then-national security adviser John Bolton. Hill is scheduled to testify publicly on Thursday.

Vindman has said he considered it inappropriate for U.S. government officials to solicit any foreign investigation into an American citizen. “If [the Ukrainians] chose to do it, they could potentially tip the scales, and this would not be a fair investigation, and it would provide, you know, compromising on maybe even fabricated information, if need be,” Vindman said in his deposition. He also warned Zelensky about “staying out of the domestic politics in the United States” when Vindman visited Ukraine as part of the U.S. delegation for Zelensky’s May 20 inaugural.

At the beginning of his testimony, Vindman put his appearance in powerful perspective: that of a Soviet refugee whose father fled 40 years ago. In Russia, he said, what he did—expressing concerns about the president and offering public testimony—”would surely cost me my life.”

“I am grateful for my father’s brave act of hope 40 years ago and for the privilege of being an American citizen and public servant, where I can live free of fear for mine and my family’s safety,” said Vindman. He added a message for his father: “Do not worry. I will be fine for telling the truth.”

Additional reporting: Erin Banco