In light of political events in America today, I thought it germane to resurrect this question.
It is strange how events that occur in just three years can drastically change the scope of a question from opinion-based to a question that has empirical evidence behind it.
I don't think anyone in 2014 could possibly have predicted the tremendous influence of social media, and in particular, Russian interference, on the American political scene. It is no longer a purely hypothetical scenario.
The answer has been proven to be 'Through intervention of public opinion through social media'. A concerted and directed dis-information campaign, directed by a centrally-organized body that has tremendous resources beyond just a political party (equivalent to the state resources of a country as powerful as Russia). A campaign that has access to an enormous data base of knowledge about the voting habits and, in fact, information on the personal habits and interests of the American public, hacked from sources as diverse as subscription lists and favorite internet sites visited. Then, using this database to specifically target social media messages to selected individuals, tailored to their fears and worries. See for instance Data of almost 200 million voters leaked online by GOP analytics firm as to how extensive this data base actually is.
In light of recent history, perhaps 2035 was overly pessimistic. But. in 2014, there were very few Americans who would ever have considered how much influence a foreign party could have on an American election. The internet, and social media, just wasn't considered a factor in any of the answers.
And in light of recent history, perhaps the door for using such techniques is rapidly closing.