The FBI is investigating whether persons involved with President Trump’s campaign collaborated with Russian officials to help Trump win the election. Let that sink in for a moment. Then take a deep breath, exhale and try to imagine where this might lead.

FBI Director James B. Comey confirmed Monday what we suspected: an active probe of Russia’s election meddling, which includes “investigating the nature of any links between individuals associated with the Trump campaign and the Russian government, and whether there was any coordination between the campaign and Russia’s efforts.”

Hours earlier, Trump had fired up his Twitter account in a vain attempt to make the whole thing go away. He began his tweet by saying, “The Democrats made up and pushed the Russian story as an excuse for running a terrible campaign.”

That was a lie, perhaps designed to reassure the president’s loyal supporters, perhaps to salve his own bruised ego. “The Democrats” didn’t make up anything. The intelligence community has reached the conclusion that the Russian government actively tried to meddle in the election — initially, perhaps, to weaken confidence in our political process, but later to boost Trump’s chances of winning.

[Republicans read Trump’s cue cards on Russia and wiretapping]

To this end, according to the intelligence assessment, the Russians hacked into the Internet communications of prominent Democrats and party institutions — including the Democratic National Committee — and orchestrated a series of leaks timed to do maximum political damage to Hillary Clinton.

It is bad enough to have to wonder whether Trump’s narrow margin of victory might have resulted from a boost provided by Russian President Vladimir Putin. It is much worse to think that anyone connected with the Trump campaign might have known about this interference by an adversarial foreign power and failed to sound the alarm — or, perhaps, even collaborated in the dark operation.

Trump pretends this is all sour grapes over Clinton’s loss, but it’s not; she didn’t win, and Democrats have moved on. It’s about what Comey called a Russian attempt to “undermine our democracy” by helping one candidate at the expense of another.

Trump also tries to change the subject by making wild and unsupported allegations, such as his ridiculous charge that then-President Barack Obama ordered wiretapping of Trump Tower during the campaign. Comey and National Security Agency Director Michael S. Rogers both testified they had no information to support Trump’s claim.

Comey added that “no president” could unilaterally order such surveillance. And Rogers flatly denied the Trump administration’s absurd fallback claim that Obama somehow arranged for British intelligence to do the snooping for him.

Throughout the hearing, Republicans sought to focus on leaks of classified information that found their way onto the front pages of The Post and the New York Times. At one point, Rep. Trey Gowdy (R-S.C.) pressed Comey on whether a journalist who published such material wasn’t guilty of committing a felony. Comey didn’t bite, apparently disinclined to threaten reporters with long prison terms.

The real issue, of course, is the information itself. Michael Flynn had to resign as Trump’s national security adviser after it was revealed that he had lied about his conversations with Russian Ambassador Sergey Kislyak. Despite what he told Congress during his confirmation hearing, Attorney General Jeff Sessions had meetings with Kislyak, as did several other Trump campaign advisers. There are numerous allegations of other contacts, which have yet to be discounted or confirmed.

[No, Republicans, the ‘real story’ is not the leaks]

Meanwhile, Trump’s rhetoric about Putin and Russia has been anomalously gentle. He does not hesitate to blast German Chancellor Angela Merkel, a staunch ally, for not spending enough on defense; he goes out of his way to bash our neighbor Mexico; and he even managed to get into a needless row with the prime minister of Australia. Yet he has consistently conveyed his admiration for Putin’s leadership and expressed a desire for a warmer U.S.-Russia relationship.

An FBI investigation, it seems to me, would necessarily have to look into the president’s business relationships with Russians tied to the Putin regime. In 2008, Donald Trump Jr. said publicly that “Russians make up a pretty disproportionate cross-section of our assets” and that “we see a lot of money pouring in from Russia.” The president now denies significant business involvement with Russians. Which is true?

If the FBI trains scrutiny on such Trump campaign figures as Paul Manafort and Roger Stone, what will they find? And why does the subject of Russia so reliably send Trump into a Twitter rage?

This trail may lead somewhere or it may lead nowhere. But now it will be followed to the end.

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