Since I can remember, manipulated elections, orchestration of military coups, foreign support of political parties, funding of terrorism, political infiltration by means of NGOs ... that's where the U.S. is the usual suspect; if not more. This is why the current self-victimization of parts of the U.S. political world, that Russian hackers would have manipulated the U.S. election, is quite amusing to me. So "the Russians" did it? Okay.
It is not easy to casually read on the topic of foreign electoral interfierance: too many conspiracy theorists and also bad journalism are in the public domain. This is why I was happy to find publications by Dov H. Levin which are related to his doctoral dissertation at UCLA, Department of Political Sciences, titled "George Washington Must Go": The Causes and Effects of Great Power Electoral Interventions and his research interest in "The causes and effects of partisan electoral interventions; Interventions (general); Regional war and peace; Nationalism, Ethnicity and conflict; Terrorism" now as a a Post Doctoral Fellow in the Institute for Politics and Strategy at Carnegie-Mellon University. He is in the process of publishing his datasets on his website (http://www.dovhlevin.com/datasets) and wrote an interesting non-academic article in the Washington Post (published September 7th, long before the current diplomatic fallout between the U.S. and Russia): Sure, the U.S. and Russia often meddle in foreign elections. Does it matter? He predicted that in this case a manipulation would not be effective because 1) it is covert, 2) foreign electoral interventions in the U.S. are historically ineffective or even counterproductive and 3) the hacking was partly exposed. In other settings a foreign interference may modify election results up to 3 %.