The standard routine for an MP defecting to another party is for members of the jilted party to demand that the turncoat submit themselves to a by-election; the MP and their new party say let’s have a general election.
This ritual has been played out many times since 1982 when Bruce Douglas-Mann defected from Labour to the new Social Democratic Party and resigned as an MP to fight the seat under his new colours. He lost to Angela Rumbold, the Conservative candidate, and for decades no defector was keen to repeat the experience.
Not until 2014, when Douglas Carswell and Mark Reckless defected from the Conservatives to Ukip, fighting and winning by-elections in their seats. They seemed to be unusual cases in the peculiar circumstances of the agitation for leaving the EU, although Reckless subsequently lost his seat in the 2015 general election.
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