It makes me think of Smeagol/Gollum figure arquetype in Lord of the Rings.

In the story, it definitely serves a purpose to be alive and not killed. And it falls upon its own weight. And it serves as a constant reminder of why the one Ring, lets say power or ruling power, can corrupt beings. So having a clown politician in tar and feathers serves more, I think, than a rolling head. A rolling head might deviate the judgement to the executioner. While clowning them lets them exist in accordance with what they are by plain resonance