Donald Trump has been loathe to admit that Russian interference had any effect on the 2016 presidential election. He is afraid that a close look at the Russian meddling in that election will show that their actions did help him to win (whether he colluded with them to accomplish that or not) -- and that would make him look undeserving of the office (since he got it with foreign help).
It turns out that his fears are well-grounded. While there's still no evidence that the Russian hacking was able to alter any votes, a new study shows that Russian trolls were effective in planting "fake news" on social media which depressed the vote for Clinton (maybe as much as 4% overall) -- and that was enough to deny her an electoral college victory.
Most of these fake stories were planted on social media by Russian "trolls". They were then picked up and redistributed widely by both Trump supporters on the right and Sanders supporters on the left. Most of those passing on the fake stories probably thought they were true, and were just trying to help their own candidate -- but that doesn't excuse their being duped by Russian trolls.
The new study was done by Richard Gunther, Paul A. Beck, and Erik C. Nesbit at Ohio State University. The whole study is well worth reading, but I provide just a tiny part of it below.