In early July, it emerged that Mr. Carlson had been trying to secure an interview with Russia’s president, Vladimir V. Putin. But in making his accusation, Mr. Carlson had not disclosed to his viewers that he had been reaching out to the Russian government via Kremlin intermediaries at the time.

That context was important. If the National Security Agency, as a matter of routine foreign intelligence-gathering, were targeting a Kremlin-linked Russian who interacted with Mr. Carlson, the agency would have incidentally gathered the communications between its target and the Fox News host without having set out to intercept any of Mr. Carlson’s private messages and without monitoring what he was saying to anyone else.

Similarly, if the agency were targeting a government official in Russia who talked about Mr. Carlson’s outreach with the intermediary he had spoken to or with anyone else, then it would have picked up information about what Mr. Carlson was saying on that topic from such discussions about him.

Update: A statement from Fox: “We are gratified to learn the NSA’s egregious surveillance of Tucker Carlson will now be independently investigated. As we have said, for the NSA to unmask Tucker Carlson or any journalist attempting to secure a newsworthy interview is entirely unacceptable and raises serious questions about their activities as well as their original denial, which was wildly misleading.”