I've been thinking more about Pain's fascinating link above
www.theatlantic.com/amp/article/530736/
and about the fake KKK story.
It's got me wondering about historical parallels. If I had to reach for a political counterpart to Putin, I think it might be the first ever chancellor of a unified Germany, Otto Von Bismarck, back in the 1870s. He famously manipulated the text of a dispatch (the Ems Telegram) and leaked the "fake news" version to the French press, precipitating a diplomatic crisis and leading to France declaring war on Prussia (a war which Bismarck knew they were in no position to win - they duly lost 7 weeks later, consolidating Bismarck's grip on power and enabling him to extend his power base to cover the other German speaking states).
When it comes to Putin and Trump, the thing that strikes me is that Putin doesn't actually need kompromat, or any solid grip on Trump himself of the sort that (if proved) might lead to Trump's impeachment (I'm pretty sure he does have some of Trump's inner circle in his pocket, but not necessarily Trump himself). The confusion of everyone wondering what the extent of the connections are and whether or not they constitute grounds, and whether we have enough evidence or not: that on its own is enough to serve Putin's purposes.
Of course, if Trump tries to obstruct an investigation into his inner circle and their Russian ties that is grounds for impeachment on the basis of obstruction of justice - but it's the sort of grounds that Trump's supporters can throw their hands up at and go "but Trump himself did nothing wrong."
For an impeachment to work it needs not just solid evidence on a charge which pretty much everyone can agree is justified grounds for impeachment, it needs to have carried enough of the public along with it (including a sufficient proportion of our Trumpette visitors) that it can be done without leading to civil unrest.
By everyone agreeing that the grounds are justified, I'm thinking of for instance the Clinton impeachment. There were a lot of your typical lefty-dude-bros whose attitude was "yes he's done it, but c'mon, get real, since when was oral sex grounds for impeachment? It's a private peccadillo, not treason FGS!" Of course it was the perjury and obstruction of justice bits which led to impeachment - which failed - not the oral sex itself. But I can imagine dyed-in-the-wool Trumpites saying similar - they'd gloss over the obstruction of justice bits and simply say "so, the guy's son-in-law has business interests in Russia? Since when have we used guilt-by-association to topple a president in the US?" Of course, this misses the point of the charges - as indeed the lefty dude bros missed the point of the charges - but it's not just facts, but the scope for different interpretations of those fact that matters.
That's why I'm back where I was at the start of this thread - thinking that any impeachment has to be done really carefully and be absolutely watertight, not leaving wriggle room for "you're just using a minor procedural point to try to bring him down for political reasons." Which is why I still think the left should be concentrating on getting their supporters out in force at the mid-terms. The democratic process looks to me a better option than impeachment at the moment.