THE NEWS that members of President Trump’s circle had repeated contacts with Russian intelligence officials in the year before the election, reported by the New York Times on Tuesday, might have been less concerning if the president had responded by explaining or condemning the contacts and accepting the need for an impartial investigation. Instead, on Wednesday morning, he dashed off a half-dozen tweets in which he curiously both denied the news and attacked the leakers who disclosed it. In so doing, he gave more cause for Republicans and Democrats to demand answers about his opaque and increasingly troubling ties with Moscow.

“The fake news media is going crazy with their conspiracy theories and blind hatred,” Mr. Trump tweeted. “This Russian connection non-sense is merely an attempt to cover-up the many mistakes made in Hillary Clinton’s losing campaign.” Then he insisted, “The real scandal here is that classified information is illegally given out by ‘intelligence’ like candy. Very un-American!”

The emerging White House line that questions about a Trump campaign-Russia connection merely reflect a war by the intelligence community on the president makes little sense. In fact, the FBI, not some rogue spy agency, has taken the lead role in investigating contact with Russian officials by associates of Mr. Trump. That would be the same agency whose questionable disclosures about its probes of Ms. Clinton’s emails may have gained Mr. Trump the presidency. Moreover, those who are properly concerned about Mr. Trump’s possible connections to the regime of Vladi­mir Putin are not mere Clinton dead-enders, but a growing and bipartisan list of senators.

To be clear, there is still plenty the public does not know. The nature of the apparent communications remains murky. Direct evidence that the Trump campaign colluded with Russian officials to sway the election continues to be lacking. But even the scant details already reported challenge previous assurances from Mr. Trump that no one on his staff had contact with the Russians during the campaign. Notably, White House press secretary Sean Spicer echoed those claims from the lectern on Tuesday just before reports emerged suggesting otherwise. His credibility, like that of the White House as a whole, has been shattered after less than four weeks on the job.

It is heartening to hear that the FBI has devoted significant resources to investigating any connections between Mr. Trump’s circle and a foreign government committed to weakening the United States and its allies. Because he was so close to the Trump campaign, Attorney General Jeff Sessions should recuse himself from any and all decisions relating to that investigation.

Still, the latest news, on the heels of the forced resignation of national security adviser Michael Flynn over contacts with the Russian ambassador, underscores the dire need for a broader, bipartisan probe of Russia’s election-year meddling. Members of the Senate Intelligence Committee insist that the panel is working diligently. But there may well be strong political pressure on Republicans to choke the investigation or to keep key findings secret. Senior House Republicans, for example, still seem uninterested in seriously probing these issues. If congressional inquiries ultimately are derailed by politics, an independent commission must be empaneled.