Donald Trump and Vladimir Putin at the G20 summit. Photo: Mikhail Metzel/Mikhail Metzel/TASS

Not long ago, it was fashionable for pundits to assert there was no evidence that the Trump campaign colluded with Russia. That line was shaky at the time, and has been quickly blown to smithereens. We have gone from evidence of collusion to proof, with emails establishing the campaign’s clear interest in accepting Moscow’s help to win the election.

This is a very simple test of the common English understanding of the term “collusion.” Your campaign is told that Russia wants to help you win the election. (“This is obviously very high level and sensitive information but is part of Russia and its government’s support for Mr. Trump.”) If you refuse to take the meeting, or perhaps take it only to angrily tell your interlocutor you want no part of the project, then it isn’t collusion. If you take the meeting on the proposed terms, you are colluding. If somehow the information on offer turned out to have no value, and the contacts went no farther, then the meeting was ineffectual collusion. But Donald Trump Jr.’s response clearly indicates that he accepted the meeting in order to collude. (“If it’s what you say I love it.”)

This is the scope of the unresolved question now. How much collusion happened?

Previous news reports have established other potential avenues for collusion. There is The Wall Street Journal reporting from June, which shows both a Republican staffer identifying himself as working for Michael Flynn trying to acquire stolen Democratic emails from Russia, and Russians working to get stolen emails to Flynn. There is also the Washington Post report from May revealing that Jared Kushner tried to establish a secret communications channel with Russia during the transition.

The revelatory emails suggest other possible channels of collusion. One email from Goldstone states, “I can send this info to your father via Rhona” — presumably Rhona Graff, Donald Trump’s personal assistant — thereby implying that President Trump may have received the information himself, and not merely through his aides. (Also, Rhona should probably hire a lawyer, if she hasn’t already.) It’s also noteworthy that Paul Manafort and Jared Kushner attended the meeting with a lawyer Trump Jr. identified as a “Russian government attorney” that was specifically dedicated to collusion.

How far the collusion went, and what elements will be provable, is hard to say. But a few larger realities are suggestive. Trump has, and many of his close advisers have, lied repeatedly about their contacts with Russia. Many of his norm-breaking actions — from the refusal to disclose the tax returns that would reveal the extent of his ties to, or dependence upon, Moscow, to his firing of Preet Bharara and James Comey — can be most rationally explained as a desire to cover the story up.

On a broader plane, Trump is a swindler who partners with mobsters and has built his life around the ethos that the logic of winning overpowers any other morality. The most sinister versions of the collusion scenario have been treated as unlikely or paranoid hypotheses. But it is the explanation most consistent with distinct sleaziness that defines Trump and which he has always looked for in his partners, from Roy Cohn to Manafort. To imagine that Trump might have had the chance to benefit politically from Russian espionage, and turned it down out of a sense of responsibility, is the unlikeliest scenario of all.