7 Bloc Québécois MPs (Québec debout crisis)

On February 28, 2018, seven of the Bloc Québécois's ten MPs left the party following leader Martine Ouellet's defeat in a leadership review referendum. The departing MPs — Michel Boudrias, Rhéal Fortin, Simon Marcil, Monique Pauzé, Louis Plamondon, Gabriel Ste-Marie, and Luc Thériault — accused Ouellet of erratic leadership and divisive behaviour. Five of them (Fortin, Pauzé, Plamondon, Ste-Marie, and Thériault) formed the short-lived "Québec debout" caucus, while Boudrias and Marcil sat as Independents. The crisis left the Bloc with only three loyal MPs, its lowest ebb in history.

Ouellet resigned as BQ leader in June 2018. Under new leader Yves-François Blanchet, all seven MPs returned to the BQ fold by September 2018. The Bloc then staged a remarkable comeback in the 2019 election, winning 32 seats. The Québec debout episode, while brief, demonstrated both the fragility of small parliamentary caucuses and the capacity for reunification when leadership disputes are resolved.