Lt. Col. Alexander Vindman, one of the key witnesses in the House Democrats’ impeachment hearings, is an Iraq war veteran and Purple Heart recipient who has served in the US Army for the past 20 years.

He also emigrated from the Soviet Union in 1979, when he was 4 years old — a fact that the attorney for House Republicans played on during a line of questioning during Vindman’s Tuesday morning’s hearing that seemed to imply he was unpatriotic and untrustworthy.

Vindman is important because he was a high-level US official on Ukraine who listened to President Donald Trump’s now-infamous July 25 call with Ukraine President Volodymyr Zelensky and, afterward, raised concerns with his superiors about the appropriateness of Trump’s “demand” (his words) that Ukraine investigate the Bidens. As a veteran, he’s one of the Democrats’ most credible witnesses — proof that Trump’s behavior really was troubling. It’s vital for the Republican cause to discredit him.

Steve Castor, the Republican attorney, tried to do this by asking Vindman about a visit to Ukraine for Zelensky’s inauguration earlier this year. He specifically focused on a job offer Vindman received from Oleksandr Danylyuk, the former head of Ukraine’s National Security and Defense Council. Apparently, Danylyuk offered Vindman an opportunity to become Ukraine’s defense minister three times during the trip — and, each time, Vindman declined.

“Upon returning, I notified chain of command and the appropriate counterintelligence folks about this, the offer,” Vindman said.

But Castor wasn’t satisfied. He continued to press Vindman on whether he ever considered the offer, resulting in an exchange in which he appeared to call Vindman’s patriotism into question:

CASTOR: Ukraine’s a country that’s experienced a war with Russia. Certainly their minister of defense is a pretty key position for the Ukrainians. President Zelensky, Mr. Danylyuk, to bestow that honor — at least asking you — that was a big honor, correct? VINDMAN: I think it would be a great honor, and frankly I’m aware of service members that have left service to help nurture developing democracies in that part of the world. It was an Air Force officer that became minister of defense, but I’m an American. I came here when I was a toddler. And I immediately dismissed these offers. Did not entertain them. CASTOR: When he made this offer to you initially, did you leave the door open? Was there a reason he had to come back and ask a second or third time? VINDMAN: Counselor, you know what, the whole notion is rather comical that I was being asked to consider whether I’d want to be the minister of defense. I did not leave the door open at all. CASTOR: Okay. VINDMAN: But it is pretty funny for a lieutenant colonel of the United States Army, which really isn’t that senior, to be offered that illustrious a position. CASTOR: When he made this offer to you, was he speaking in English or Ukrainian? VINDMAN: He is an absolutely flawless English speaker.

Castor is arguing that Vindman’s loyalties were strained by repeated job offers from the Ukrainians, highlighting Vindman’s Ukrainian language skills, reminding everyone that he’s foreign-born. The insinuation, that Vindman’s background makes him an unreliable witness to Trump’s malfeasance, is reasonably clear.

Vindman himself brought up his immigrant background in his opening testimony to highlight his loyalty to the United States, explaining his decision to join the military as a way of giving back to a country that took him in after he fled Soviet totalitarianism. It was a moving story, a preemptive defense of his commitment to his country that by all rights should not have been necessary.

And yet, at the end of the questioning, Castor all but openly accused Vindman of being compromised.

“Did you ever think that possibly, if this information got out, that it might create at least the perception of a conflict?” Castor asked. “The Ukrainians thought so highly of you to offer the defense ministry post. ... But on the other hand, you’re responsible for Ukrainian policy at the national security counsel.”

Castor never outright brought up Vindman’s Ukrainian origin (or his Jewish background), but he didn’t really need to. The line of questioning served only to suggest that a Ukrainian-born immigrant cannot be trusted to be loyal to the United States even if he was wounded fighting for his country.

This line of argument was deployed by some in the right-wing media when Vindman first emerged as a key witness, like Fox News host Laura Ingraham, but seemed largely abandoned after a significant public backlash.

Castor seemed to be working to bring it back into the conversation, a move correctly diagnosed by Rep. Jim Himes (D-CT) in his questioning of Vindman later in the hearing: Castor’s line of questioning, Himes said, “was designed exclusively to give the right-wing media the opportunity to question your loyalties.”

Correction: Due to a transcription error, the initial version of the Castor-Vindman exchange transcribed above misattributed a line from Vindman’s answer to Castor’s question.