What is party discipline in the Canadian House of Commons?

Party discipline in the Canadian House of Commons is the convention that MPs vote in line with their party's position on most issues. Party discipline in Canada is significantly stronger than in the United States Congress and most other Westminster democracies. Each party has a Whip (a senior MP responsible for managing voting and attendance) and party expectations for caucus loyalty.

The strength of party discipline reflects several features of Canadian Westminster government. First, the confidence convention: a federal government depends on the support of its caucus for confidence votes; widespread caucus rebellion would risk bringing down the government. Second, the Prime Minister's appointing power: the Prime Minister appoints Cabinet ministers and Parliamentary Secretaries from caucus, giving loyal MPs significant career incentives. Third, the Prime Minister's ability to deny party candidates' nomination papers (under the Canada Elections Act, party leaders sign candidate nomination papers, giving them a final veto over candidate nominations).

Some votes are designated 'free votes' or 'conscience votes' where MPs vote according to their personal beliefs rather than party position. Major Canadian free votes have included the 1988 abortion-law debate, the 1990 Bill C-43 abortion vote (which tied 43-43 in the Senate, defeating the bill), the 2005 Civil Marriage Act (the Liberal government allowed a free vote), and the 2016 Bill C-14 medical-assistance-in-dying legislation. Some parties (notably the federal NDP) historically allow more free votes than others.

Crossing the floor (an MP joining another party or sitting as an independent after being elected for one party) is the most dramatic break with party discipline. Notable floor-crossings include Jenni Byrne (Conservative to Liberal in 1948), Lucien Bouchard (PC to founding Bloc in 1990), Belinda Stronach (Conservative to Liberal in May 2005, decisive in saving Paul Martin's government), David Emerson (Liberal to Conservative in February 2006), Garth Turner (Conservative to Liberal in 2007), Eve Adams (Conservative to Liberal in 2015), Jane Philpott and Jody Wilson-Raybould (Liberals to Independents in 2019 over the SNC-Lavalin affair), and Han Dong (Liberal to Independent in 2023). Bill C-251, introduced by NDP MP Murray Rankin in 2014, would have required MPs who cross the floor to resign and seek re-election (the bill was not adopted).