Putin/Trump: Yes, it's a thing
http://talkingpointsmemo.com/edblog/trump-putin-yes-it-s-really-a-thing
To put this all into perspective, if Vladimir Putin were simply the CEO of a major American corporation and there was this much money flowing in Trump's direction, combined with this much solicitousness of Putin's policy agenda, it would set off alarm bells galore. That is not hyperbole or exaggeration. And yet Putin is not the CEO of an American corporation. He's the autocrat who rules a foreign state, with an increasingly hostile posture towards the United States and a substantial stockpile of nuclear weapons. The stakes involved in finding out 'what's going on' as Trump might put it are quite a bit higher.
There is something between a non-trivial and a substantial amount of circumstantial evidence for a financial relationship between Trump and Putin or a non-tacit alliance between the two men. Even if you draw no adverse conclusions, Trump's financial empire is heavily leveraged and has a deep reliance on capital infusions from oligarchs and other sources of wealth aligned with Putin. That's simply not something that can be waved off or ignored.