retraction of vote with a new vote solves this.
Since I'm able to retract my vote, I cannot sell it. And since I can retract my vote, I cannot be coerced in any way.
Elections results have to be final at some point, and after that point no further retraction/changes can be made, therefore you can be coerced.
Elections results have to be final at some point, and after that point no further retraction/changes can be made, therefore you can be coerced.