Duverger's Law describes tendencies, not inevitabilities. Canada has FPTP and several parties in Parliament. UK the same. A regional split in the party system,

Duverger's Law describes tendencies, not inevitabilities. Canada has FPTP and several parties in Parliament. UK the same. A regional split in the party system, or a conservative insurgency against the Republicans in Alabama, or a liberal one against the Dems in DC, or any one of a number of other scenarios would do it.