If the middle class as a big group spanning the median (of the voting public) is destroyed or diminished so that it no longer spans the median, the median will still matter but would move down in income and presumably be more radical.

Example: a society with three classe, 4% rich, 16% middle and 80% poor needs to keep the poor from voting or making sure their votes don't count as much. 19th century Prussia solved this by formalising the groups and giving them 1/3 of the seats each.

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