The Mueller investigation has been an unmitigated success in exposing political corruption. In the case of Paul Manafort, the corruption was criminal. In the case of Trump, the corruption doesn’t seem to have transgressed any laws. As Michael Kinsley famously quipped, “The scandal isn’t what’s illegal; the scandal is what’s legal.” Lying to the electorate, adjusting foreign policy for the sake of personal lucre, and undermining an investigation seem to me pretty sound impeachable offenses—they might also happen to be technically legal.

Through his investigation, Mueller has also provided a plausible answer to the question that first bothered me. Trump’s motive for praising Putin appears to have been, in large part, commercial. With his relentless pursuit of Trump Tower Moscow, the Republican nominee for president had active commercial interests in Russia that he failed to disclose to the American people. In fact, he explicitly and shamelessly lied about them. As Trump’s former personal attorney Michael Cohen implied in his congressional testimony, Trump ran his campaign as something of an infomercial, hoping to convince the Russians that he was a good partner. To enrich himself, Trump promised to realign American foreign policy.

David Frum: The question the Mueller report has not answered

This is the very definition of corruption, and it provides the plot line that runs through the entirety of Trump’s political life. The president never chooses to distinguish—and indeed, may be temperamentally incapable of distinguishing—his personal interests from the national interest. Why has he failed so consistently to acknowledge Russian interference in the election? Because that interference was designed to benefit him. Why did he fire James Comey and, let’s use the word, obstruct the investigation into election interference? Because he wanted to protect himself from any investigation that might turn up material that reflected badly on him and his circle. (And whatever Mueller’s ultimate conclusion about collusion, his investigation has proved to be an unending source of damning revelations about the president and the men who constituted his closest advisers. )

Along with Trump’s stalwart defenders, many left-wing critics of hawkish foreign policy have been quick to tout Attorney General William Barr’s letter as exoneration. Matt Taibbi has compared the coverage of the Russia scandal to the media’s gullible reporting about Iraqi weapons of mass destruction. The accusation is that the media are prone to parrot whatever self-serving conspiracy the national-security state has to offer. But Mueller has apparently endorsed the fundamental underlying case emanating from the intelligence community: The Russians were actively working to secure Trump’s victory. What makes their interference so horrifying is that it involved the theft of information and the active manipulation of public perceptions. All of that is arguably far worse than Watergate.