Perhaps the most memorable moment of the early portion of Lt. Col. Alexander Vindman’s testimony to impeachment investigators on Tuesday came when he clapped back at House Intelligence Committee ranking member Devin Nunes (R-CA) for calling him “Mr. Vindman” instead of by his military title.

“Ranking member, it’s Lieutenant Colonel Vindman, please,” Vindman said.

But the broader context of that moment is significant, coming as it did amid a line of questioning from Nunes that seemed aimed at outing the intelligence community whistleblower who first sounded the alarm about President Donald Trump’s dealings with Ukraine.

Nunes did not defend Trump’s conduct on the merits. Instead, he used his time to push the very same conspiracy theories about the Bidens that Trump tried to leverage the Ukrainian government into validating with investigations, grill both Vindman and Pence aide Jennifer Williams about whether they leaked to the media, and raise questions about why Vindman was reluctant to answer questions that could out the whistleblower.

Nunes suggests Vindman should take the 5th if he won't answer questions about the whistleblower. Vindman's lawyer interjects to point out that his client is just following the rules. (Note that there's a guy with a MAGA hat sitting behind Vindman's lawyer.) pic.twitter.com/GBG8u4ryKR — Aaron Rupar (@atrupar) November 19, 2019

According to the whistleblower complaint, the whistleblower himself was not on the call, but spoke to “multiple White House officials with direct knowledge of the call.” That would include National Security Council officials like Vindman. And that appears to be why Republican questioners asked whom Vindman had talked to about the call.

Vindman said the only two individuals he told about the call outside the NSC staff, both of whom were fully cleared and needed to know, were State Department official George Kent, and a member of the intelligence community. (The whistleblower is reportedly a CIA officer.)

So Nunes demanded to know the name of that person — but Vindman’s lawyer objected, and Intelligence Committee Chair Adam Schiff (D-CA) cut off the questioning, deeming it an effort to out the whistleblower.

Vindman said he does not “know” who the whistleblower is, but it is possible he suspects the whistleblower is the person he talked to. Another possibility is that he is just generally avoiding naming members of the intelligence community, since it’s well-known that the whistleblower is one.

Although, as Schiff pointed out during Vindman’s exchange with Nunes, the whistleblower is legally protected from reprisals, that doesn’t mean he wouldn’t face retaliation — professional or personal — if his name became known. Moreover, Nunes’s line of questioning is beside the point. The whistleblower’s complaint about how Trump tried to leverage the Ukrainian government into doing political favors for him has been corroborated both by the White House and by a number of witnesses who have testified before impeachment investigators.

As unseemly as Nunes’s line of questioning was, it arguably wasn’t the low point of Tuesday’s hearing for Republicans. Later on, Republican counsel Steve Castor highlighted Vindman’s good relations with Ukrainian government officials in an apparent effort to draw patriotism into question.

Castor highlights Lt. Col. Vindman's ties with Ukraine in an attempt to draw his patriotism into question pic.twitter.com/vYvUH06Utn — Aaron Rupar (@atrupar) November 19, 2019

Vindman, during his powerful opening statement, emphasized that he came forward to government officials regarding his concerns about Trump’s dealings with Ukraine out of a sense of duty to the country.

Listen to Today, Explained

Don’t have time to watch the impeachment hearings live? Tune into Today, Explained — Vox’s daily explainer podcast — to get the most important takeaways in just 20 minutes.

Subscribe to Today, Explained wherever you get your podcasts, including: Apple Podcasts, Google Podcasts, Spotify, Stitcher, and ART19.