REP. DEVIN NUNES (R-Calif.) on Monday denounced what he described as the illegal leak of classified information concerning conversations between associates of Donald Trump and Russian officials. He insisted that those who described those contacts to the press be tracked down and prosecuted. He demanded that FBI Director James B. Comey confirm that such revelations “violate . . . a section of the Espionage Act that criminalizes the disclosure of information concerning the communication and intelligence activities of the United States.”

Forty-eight hours later, Mr. Nunes himself held a news conference in which he cited a confidential source to describe what clearly appeared to be classified information about intercepted communications involving Trump associates. He did this outside the White House, where he had rushed to brief the president about the intercepts — even though the House Intelligence Committee he chairs is supposed to be investigating the Trump campaign’s possible connections with Russia.

We’ve said before that it was doubtful that an investigation headed by Mr. Nunes into Russia’s interference in the election could be adequate or credible. The chairman’s contradictory and clownish grandstanding makes that a certainty. His committee’s investigation should be halted immediately — and Mr. Nunes deserves to be subject to the same leaking probe he demanded for the previous disclosures.

Mr. Nunes’s behavior provoked head-scratching from Republican colleagues, in addition to denunciations from Democrats; Sen. John McCain (R-Ariz.) called it “bizarre.” But there was nothing really irrational about the representative’s actions: He was simply doing everything in his power to protect President Trump, for whom he has become a fierce, if erratic, guard dog. In denouncing leaks Monday, Mr. Nunes was doing his best to deflect attention from what appears to be a substantial ongoing FBI investigation into whether members of the Trump campaign colluded with Russia.

In offering his own leak Wednesday, Mr. Nunes was trying to provide cover for Mr. Trump’s false claim that his campaign had been wiretapped on orders of President Barack Obama — a statement that Mr. Comey flatly described as groundless. Unsurprisingly, Mr. Trump declared hours later — again, falsely — that Mr. Nunes had proved him right.

In fact, as Mr. Nunes himself acknowledged, the intercepts he described were legal and appropriate, the result of routine surveillance of foreign targets, or that were approved by a secret court. The identities of the Americans who were picked up in the conversations were mostly masked — Mr. Nunes said he was able to figure out they were Trump associates because of the context. Quite possibly, the chairman revealed the same intelligence that sources described to The Post when it reported on conversations between Michael Flynn, then Mr. Trump’s nominee for national security adviser, and Russian Ambassador Sergey Kislyak — a disclosure Mr. Nunes tarred as criminal.

Mr. Nunes’s antics serve only to underline the urgency of a serious, nonpartisan and uncompromising investigation into Russia’s interference in the election and any contacts between Moscow’s agents and the Trump campaign. The Senate Intelligence Committee, which is also conducting a probe, may make a useful contribution, but as Mr. McCain said, “no longer does the Congress have the credibility to handle this alone.” It is time to discuss the formation of an independent, nonpartisan commission with full subpoena power, like those that investigated the attacks of 9/11 and the intelligence failures in Iraq. In the meantime, House leaders should put an end to the embarrassing travesty being directed by Mr. Nunes.