The one major exception occurred during the prime ministership of Pierre Elliott Trudeau, Justin Trudeau’s father. In 1980, the elder Trudeau was returned to office after a brief spell in opposition.

Chrystia Freeland, the former deputy prime minister, sought to distance herself from Mr. Trudeau in a public letter criticizing him for “costly political gimmicks.”

In the days since Prime Minister Justin Trudeau announced he'll be stepping down as leader, the list of potential candidates to replace him has considerably thinned. Here's a look at who's declared their intentions,