If the candidates were open and transparent AND if voters only cared about ability to govern, then no one could influence the election. But that isn't going to happen. But labor unions by far and away have the largest influence vector for elections, followed by large corporations. Large corporations by the amount of money they contribute, usually have more influence on a continuing basis, but often hedge their bets by donating to both sides in the election. Lately though some large entities (I'm looking at you Facebook!) have stopped any pretense of neutral news reporting and might as well be looked upon as strictly aligned with particular candidates. Labor unions strongly influence elections by the sheer number of their Sheeple following the edicts of their labor union "bosses". Not to say all do, but a large enough number to sway some elections. If all candidates where required to be open and transparent and there was a mechanism to expose when they weren't and if so called fact finding organizations where unbiased and not supportive of any particular candidate, and news organizations were actually news organizations, not thinly veneered arms of entities with a political agenda then the voters would be presented with a neutral view that was unbiased to choose from. Foreign governments influence on American elections is a "red" herring. The domestic influencers actually do influence the outcome.