What is it that Putin has over Trump?

I'm betting that it's The Donald's involvement in the laundering of Russian money through New York real estate (a well-known pipeline for oligarch billions looking for a safe home in the west).

Trump has a long history with Russia, having done business there for some thirty years.

That, of course, would explain the adamant refusal to release his tax returns.

Of course, there could be much else, as hinted in the Steele dossier, and I wouldn't exclude more salacious later material, but I'm guessing it began with the washing of rubles by the Trump Organization...