President Donald Trump wants the issue of Russian influence in the 2016 election to vanish. He has called it “a hoax” in his tweets But it’s not. It’s real – and might take years to resolve.

FBI Director James Comey testifies before the House Intelligence Committee hearing into alleged Russian meddling in the 2016 U.S. election, on Capitol Hill in Washington, U.S., March 20, 2017. REUTERS/Joshua Roberts

The Federal Bureau of Investigation has been on the case since July. Its chief, James B. Comey, is creating a headquarters task force to coordinate the work of at least three field offices to find the facts. The federal investigators, and platoons of the nation’s best journalists, have a long battle ahead.

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Comey made clear to the House Intelligence Committee that this is a spy-catching case, involving Russian intelligence and suspected American agents of influence. It takes time to solve such mysteries. The FBI spent two decades uncovering a Russian mole in its own ranks.

And this investigation is more complex than Watergate, a domestic case of political espionage that took more than two years before it felled President Nixon. It’s more intricate than the Iran-Contra imbroglio, when the Reagan administration sold weapons to Tehran and slipped the profits to Central American rebels, and which took six years to conclude in court.

The Russia case, like Watergate, starts with a break-in at Democratic headquarters – only Moscow did it, virtually, with cyberwarfare. Like Iran-Contra, it involves interplay among foreign agents and the National Security Council – in this case, retired Lt. Gen. Michael T. Flynn, the cashiered NSC director.

Flynn has offered to tell his version of the story to the congressional intelligence committees in exchange for immunity from criminal prosecution. I would not necessarily take him at his word. At the last job he lost, running the Defense Intelligence Agency, his subordinates called his version of the truth “Flynn facts” – untruths.

Here’s one indisputable fact: Flynn was paid by firms linked to Russia, including the state-run RT TV, and failed to disclose those payments in official White House financial forms filed in February, right before he was fired.

Here’s another: He was let go for misleading Vice President Mike Pence about his conversations during the presidential transition with Russian ambassador Sergei Kislyak.

These included five phone calls on Dec. 29, the day the United States retaliated for Moscow's meddling in the election. He denied discussing the thorny issue of sanctions with Kislyak, although he did just that. Three years ago, President Barack Obama imposed severe economic sanctions on Russia for seizing Crimea and threatening Ukraine, both territories of the old Soviet Union. These measures targeted Moscow’s financial institutions and Russian leader Vladimir Putin’s inner circle – the oligarchs. Putin wants these sanctions to vanish.

Why have key members of Team Trump, including Attorney General Jeff Sessions and presidential son-in-law and senior adviser Jared Kushner, kept their lips zipped about their meetings with Team Putin? And why is Trump denying that the “Russia story” is a reality – other than to quash the idea that Moscow wanted him to win the election?

Be prepared for an epic struggle before we have straight answers.

The House Intelligence Committee’s investigation has been derailed. The Republican chairman of the committee, Devin Nunes, has canceled or postponed key hearings. He has undermined himself by reviewing classified documents on White House grounds, discussing the reports with Trump while stiff-arming the committee’s top Democrat, then misrepresenting the fact that he got the documents from a former counsel to the committee, now a White House lawyer, and the senior director for NSC intelligence. A Democratic member of the intelligence committee warned: “This is what a cover-up to a crime looks like.”

What crime? We may not know for many months if one exists. If Flynn knows, and if he wants to barter for immunity, he had better be ready to deliver evidence directly to the FBI that people above his pay grade were party to a conspiracy.

Comey and his FBI agents are out to gather evidence that could be used in a court of law against members of Team Trump. It will be extraordinarily difficult: cases touching on international espionage, electronic eavesdropping, political warfare, or the power of the president can involve information too sensitive to reveal at trial.

But the FBI went after Nixon and Watergate, the Reagan administration and Iran-Contra, and Bill Clinton respectively – toppling a president, winning indictments against top national security aides, and bringing evidence that led to an impeachment.

The president of the United States may think it’s fake news, but it’s the truth. The FBI is not going to let this case go away. And its investigation may last as long as the Trump administration.