I read a story yesterday from a British website I've never heard of citing an unnamed lawyer that Cambridge Analytica had the leaked Hilary emails a month before they were leaked and by extension so did the Trump campaign. That's too many caveats to post the article but I'm inclined to think it's plausible. I'll post it as a comment

https://www.spectator.co.uk/2018/06/what-does-the-british-government-know-about-trump-and-russia/