OTTAWA - On Thursday, Michael Ma became the second Conservative MP to cross the floor to the Liberal caucus in as many months.

Ma's decision to join the government, following Nova Scotia MP Chris d'Entremont's surprise floor-crossing in early November, brought Prime Minister Mark Carney's minority government to within one seat of a majority for the first time since the spring election. It also ramped up speculation about who might be next.

Switching parties between elections is a controversial practice. Still, more than 300 members of Parliament have changed parties while in office since 1867.

The first known MP to cross the floor was Stewart Campbell, a Nova Scotian who, in 1868, left the Anti-Confederates for the Liberal-Conservatives under Sir John A. Macdonald. The Dictionary of Can

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