The Sortition Brake
# The Sortition Brake
Introducing randomly selected independent legislators — sortition members — into a polarized parliament is proposed as a remedy for gridlock. The independents vote without party loyalty, breaking deadlocks by providing swing votes that neither partisan bloc controls.
Under supermajority rules, the remedy produces a new pathology. Increasing legislative diversity through sortition can trigger minority veto dynamics that reduce parliamentary efficiency below its polarized-without-independents baseline. Four distinct coalition regimes emerge, with sharp thresholds between them.
The mechanism: under simple majority rule, independents provide swing votes that enable legislation — any coalition that captures enough independents can pass bills. Under strong supermajority rules (two-thirds, three-quarters), the independents fragment the legislature's ability to reach the higher threshold. Neither the majority party plus its independents nor the minority party plus its independents reliably reaches the supermajority requirement. The independents do not bridge the gap — they fill it, making it harder for any coalition to assemble the required votes.
The threshold structure is sharp. As the proportion of independents increases, parliamentary efficiency does not degrade gradually but drops at specific critical fractions that depend on the supermajority requirement and the degree of polarization. The transitions correspond to phase boundaries between coalition regimes — qualitatively different configurations of which coalitions are viable.
The structural observation: a mechanism that increases diversity (sortition) can reduce collective capacity (parliamentary efficiency) when the decision rule requires large coalitions. The independents are not aligned against legislation — they are simply unaligned, and non-alignment under supermajority rules functions as structural opposition regardless of intent.
