WASHINGTON -- Winston Churchill famously described Russia as "a riddle wrapped in a mystery inside an enigma." The same might be said -- and the Russia reference is no coincidence -- of Paul Manafort and the trial now underway of President Trump's former campaign chairman.

The riddle, of course, is why there is a trial at all. Given the strength of the documentary evidence against Manafort -- millions in income stashed in overseas accounts and not reported to the Internal Revenue Service; doctored financial statements designed to obtain otherwise unavailable mortgages -- why did he not cut a deal with prosecutors?

Manafort is doing the legal equivalent of trying to shoot the moon -- twice. Even if he is acquitted in this case, another trial looms next month on separate charges of money laundering and failing to register as a foreign agent. Perhaps Manafort is angling for a presidential pardon. But even assuming Trump is willing to commit an act so blatantly self-interested, if not outright corrupt, a pardoned Manafort could still be compelled to testify, and prosecuted for any ensuing perjury unless Trump is so brazen as to prospectively pardon that conduct as well.

The mystery -- a mystery to me at least -- is comprehending the magnitude of Manafort's greed. Assuming the allegations are true -- and even if Manafort's former partner, Rick Gates, is an admitted liar, bank accounts don't lie -- why would someone who vacuumed up so many millions of dollars take the risk of not paying the taxes due on that income?

The Manafort indictments detail a gusher of cash flowing to the lobbyist, $60 million from the Russian-backed political party in the Ukraine alone, according to a filing by special counsel Robert S. Mueller III. Even if you paid half of that in tax, which would mean you had a pretty bad set of tax accountants, you would have enough left for all the ostrich jackets a man might want. In this case, greed isn't good -- it's stupid. The temptation to do the dirty work of autocrats and oligarchs and rake in millions in return is understandable, if not laudable; it is a bipartisan failing of human nature.

But to take the additional, risky step of tax fraud? My colleague Catherine Rampell has noted the dwindling number of prosecutions for white-collar crime, and maybe, absent Manafort's seemingly reckless decision to go to work for the Trump campaign, he might have gotten away with it. Criminal prosecutions referred by the Internal Revenue Service to the Justice Department have fallen by half from their level five years ago. Still, Manafort should not have been sleeping soundly, in any of his many multimillion-dollar homes -- he was being interviewed by FBI agents about his "offshore consulting activities" even as he was allegedly failing to report his income.

Finally, the enigma at the heart of it all: What, if anything, does this all have to do with Russia? Perhaps nothing, as Trump constantly asserts. And yet, the evidence presented at his trial demonstrates, by the time Manafort went to work for Trump -- for free! -- he was a man in dire financial straits.

As The New Yorker's Adam Davidson summarized Manafort's precarious situation and frantic behavior, "By early 2016, the man who previously had been sending hundreds of thousands of dollars to the U.S. each month seemed to be in a self-destructive frenzy, making the desperate moves of a man who needed some cash, right away, and had run out of options."

That raises the question: If Manafort was willing to go to such extreme lengths to keep himself afloat, what might he have been willing to do at the helm of the Trump campaign? We already know that Manafort was eager to use his Trump connection to "get whole," as he put it, with Russian oligarch Oleg Deripaska, who had loaned Manafort $10 million. Manafort, through an associate suspected of ties to Russian intelligence, offered Deripaska "private briefings" on the race.

It does not seem far-fetched to ask if there is anything else -- or to think that, if there is, Mueller and his team already know it. Which might explain, at least in part, the president's evident and growing agitation. And which brings us back to the lesser known ending of Churchill's quote about divining Russia's intent. "But perhaps there is a key," Churchill concluded. "That key is Russian national interest."

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