On Monday, when the House Intelligence Committee held its first public hearing about Russian involvement in the U.S. Presidential election, Republican members were almost completely focussed on leaks.

In his opening statement, Devin Nunes, the chairman of the committee, made clear how important the issue was to the G.O.P. “Who has leaked classified information?” he asked. “We aim to determine who has leaked or facilitated leaks of classified information so that these individuals can be brought to justice.”

Republicans were especially agitated about whether any former Obama Administration officials leaked information from classified transcripts of conversations between Michael Flynn, President Trump’s former national-security adviser, and Sergey Kislyak, the Russian Ambassador to the United States, during the Presidential transition. At one point, Trey Gowdy, the Republican from South Carolina best known for his investigation of Benghazi, pressed James Comey, the F.B.I. director, on whether reporters might be jailed for publishing classified information.

“Director Comey, you and I were discussing the felonious dissemination of classified material during the last round,” he said. “Is there an exception in the law for current or former U.S. officials who request anonymity?” Comey said that there was not, and Gowdy asked, “Is there an exception in the law for reporters who want to break a story?” (To his credit, Comey said, “That's a harder question.”)

With all the focus by Republicans on leaking classified information, Democrats on the committee were stunned when, in one little-noticed moment during the five-hour hearing, a prominent Republican seemed to let slip what two members of the panel told me was a piece of classified information.

Last year, the intelligence community, which consists of sixteen U.S. entities that collect secret information, produced classified and unclassified versions of a report on the Russian influence campaign during the election. The unclassified report makes bold conclusions about Russian intentions. “We assess Russian President Vladimir Putin ordered an influence campaign in 2016 aimed at the US presidential election. Russia’s goals were to undermine public faith in the US democratic process, denigrate Secretary Clinton, and harm her electability and potential presidency,” the report said. “We further assess Putin and the Russian Government developed a clear preference for President-elect Trump. We have high confidence in these judgments.”

The conclusions were unambiguous, but the evidence in the unclassified report was unsatisfying. Republicans have questioned whether Putin really had a clear preference for Trump rather than simply a general animosity toward Hillary Clinton. Members of the committee were pressing Comey and Rogers on this point when a behind-the-scenes fight that was previously classified spilled into public.

Representative Devin Nunes, of California. PHOTOGRAPH BY MARK PETERSON / REDUX FOR THE NEW YORKER

It started when Nunes asked, “Do Russians historically prefer Republicans to win over Democrats?” Nunes ticked through some recent elections and inquired whether the Russians supported John McCain over Obama, in 2008, or Mitt Romney over Obama, in 2012. Comey said that he didn’t know the answer.

“I'm just asking a general question,” Nunes said. “Wouldn't it be a little preposterous to say that, historically, going back to Ronald Reagan and all that we know about maybe who the Russians would prefer, that somehow the Russians prefer Republicans over Democrats?”

Watching the hearing, this seemed like a curious line of questioning. Because members of the House Intelligence Committee often know a great deal more than they can say publicly, they sometimes use their questioning to hint at what they have learned in classified settings. Nunes’s questions seemed to suggest some broader debate, as Comey confirmed when he shut down the exchange.

“I'm not going to discuss in an unclassified forum,” he said. “In the classified segment of the reporting version that we did, there is some analysis that discusses this because, remember, this did come up in our assessment on the Russian piece.”

Nunes thanked him and turned to Representative Peter King, of New York. King was less circumspect than Nunes had been. “I would just say on that because, again, we're not going into the classified sections, that indicating that historically Russians have supported Republicans, and I know that language is there, to me puts somewhat of a cloud over the entire report,” King said.

I didn’t notice it at the time, though I was in the room, and the C-SPAN video of the hearing doesn’t capture it, but Democrats told me that there was, at this point, a minor commotion on the dais. King had just revealed that the classified version of the report had concluded “that historically Russians have supported Republicans.”

Two Democrats, confirming what King said, told me that there was a significant fight over this judgment during a recent classified briefing. “I was really taken aback that it came up in the hearing,” one Democratic congressman on the committee told me. “I might just observe to you, if there was such a conclusion, you can bet that the Republicans would have pushed back very, very hard about such a conclusion. And I don’t want to say more than that.”

Sometimes it’s difficult for someone privy to classified information to keep straight what is classified and what is not, especially when a classified judgment seems relatively innocuous. I asked King about the exchange, and his answer suggested that he was confused about the classification.

“I have to watch myself,” he told me. “I think it was in the public report that came out, the unclassified report, that there was a finding in there that historically—so don’t quote me on this, O.K.? Because I’m not sure if this was the classified or the unclassified, but there was a conclusion that historically the Russians have favored Republicans.” I could not find that conclusion in the public report, and, as others confirmed, it was a classified judgment.

Setting aside the issue of whether it was appropriate for King to allow this piece of classified information to become public, King and the Republicans do indeed have good reason to question the intelligence community’s judgment.

“We certainly disagreed. It’s been brought up in classified hearings,” King told me. He said that his intention at Monday’s hearing “was to show how much of a bias is there in the report. If they went out of their way to say that the Russians favored Republicans historically, was that indicating that they were either pressured or were trying to find a way to make a more convincing case for Trump over Clinton?”

It’s a fair question. I asked Oleg Kalugin, a former K.G.B. general who now lives in Virginia, about the intelligence community’s alleged claim that Russia has historically supported Republican Presidential candidates. “No, that’s not true,” he told me. He said that, when he was a press officer at the Soviet Embassy, during the Nixon era, it was part of his job to send daily reports to Moscow on American Presidential elections. “We always supported the Democrats. The Soviets, and the Russians after the collapse of the U.S.S.R., have been essentially in favor of the Democratic Party, because it represented the more moderate part of the United States' political life, while the Republicans are more reactionary. The Republicans are viewed as more aggressive and anti-Communist, and that’s why the Soviets and, subsequently, the Russians would rather deal with the Democrats.” Almost everyone agrees that this calculus changed with respect to the race between Clinton, whom Putin personally despised, and Trump, who in public statements was loudly pro-Putin.

Does this debate matter? Perhaps. One of the mandates of the House Intelligence Committee is to evaluate the credibility of the intelligence community’s conclusions about Russia’s intentions last year. The intelligence community is highly confident that Putin specifically wanted a Trump victory. Republicans are skeptical and will continue to seize on this historical judgment to undermine the broader conclusions.

King said that it made him question the whole report. “That indicated to me that somewhere there was a push to really firm up their conclusion that not only did they not want Hillary but that they wanted Trump,” he said. “To me, the evidence doesn’t back that up.”