There was an American sci-fi short story, where there was an Earth-wide swing voting on something. It went with perfect equilibrium until the very end.
And there was one single man left who did not vote yet. He tried to hide from both parties, until got caught by both at once.
In the end he stands in a voting booth with both sides escalating threats to him and cries.
"Franchise" by Isaac Asimov seems the likely suspect. I originally had thought of the movie Swing Vote but its Wikipedia page led me to this story.
The story centers around Norman Muller of Bloomington, Indiana, the man chosen as "Voter of the Year" in the 2008 U.S. presidential election. Although the law requires him to accept the dubious honour, he is not sure that he wants the responsibility of representing the entire electorate, worrying that the result will be unfavorable and he will be blamed.
What do you think of the price of eggs? - in Asimov's story the man is not in position to make conscious choice about voting, the voting it automagically deduced from seemingly unrelated questions. Thus he also is not pressed by parties - would they even want to, they would still not know what to press for. In the story I remember - the plot consisted exactly of building up more and more pressure, forcing "simple man" into the dead-end, where voting for either of two politicians would result in severe if unlawful punishment, making it impossible even to just cave in.