that plan relies on Harry realizing that Malfoy thinks he's Voldemort.

... I genuinely didn't think of the Voldemort angle. That only sweetens the pot. I think that ArisKatsaris's solution is far more effective/elegant than my own. (Especially since it's foreshadowed by the part about how Harry thought of the Wizengamot as 'wallpaper' and that 'this would change'. -- that could be viewed as a dropped-hint that the solution lies in manipulating the votes. I can't think of another way Harry could achieve that than through the former Death Eaters.)