Last April, the CIA director was shown intelligence that worried him. It was - allegedly - a tape recording of a conversation about money from the Kremlin going into the US presidential campaign.
It was passed to the US by an intelligence agency of one of the Baltic States. The CIA cannot act domestically against American citizens so a joint counter-intelligence taskforce was created.
The taskforce included six agencies or departments of government. Dealing with the domestic, US, side of the inquiry, were the FBI, the Department of the Treasury, and the Department of Justice. For the foreign and intelligence aspects of the investigation, there were another three agencies: the CIA, the Office of the Director of National Intelligence and the National Security Agency, responsible for electronic spying.
Lawyers from the National Security Division in the Department of Justice then drew up an application. They took it to the secret US court that deals with intelligence, the Fisa court, named after the Foreign Intelligence Surveillance Act. They wanted permission to intercept the electronic records from two Russian banks.
Their first application, in June, was rejected outright by the judge. They returned with a more narrowly drawn order in July and were rejected again. Finally, before a new judge, the order was granted, on 15 October, three weeks before election day.
Neither Mr Trump nor his associates are named in the Fisa order, which would only cover foreign citizens or foreign entities - in this case the Russian banks. But ultimately, the investigation is looking for transfers of money from Russia to the United States, each one, if proved, a felony offence........................
A lawyer- outside the Department of Justice but familiar with the case - told me that three of Mr Trump's associates were the subject of the inquiry. "But it's clear this is about Trump," he said.
Michael Hayden, former head of both the CIA and the NSA, simply called Mr Trump a "polezni durak" - a useful fool.
The background to those statements was information held - at the time - within the intelligence community. Now all Americans have heard the claims. Little more than a week before his inauguration, they will have to decide if their president-elect really was being blackmailed by Moscow.