There are lots of state-sponsored efforts to try to influence elections in other countries and in their own countries. There are lots of non-state-sponsored organizations that are also trying to do the same, and do so by trying to spread mis- and disinformation.
It's certainly not any one actor. If asked to name the primary one, I would say Russia, as I did when I was asked earlier, but in general, there are as many opportunities as there are users of the Internet in some respects.