NDP Leader Jagmeet Singh has vowed he will help defeat the governing Liberals in a confidence vote when the House returns. The Conservatives, locked firmly ahead in the polls, have been demanding an election all fall, while the Bloc has also recently called for an election early in the new year.

Singh could still change his mind and many scenarios remain possible, such as an opposition party negotiating a big-ticket item into the budget then having a fall election as scheduled, but that's looking less and less tenable.

"It no longer makes a whole lot of sense to cut some sort of a deal and be a partner to the government that you're about to vilify a couple of months later as Public Enemy no. 1," Baran said.

A leadership race would be a hurried affair compared to Liberal party contests in the past. When Trudeau was elected leader in 2013, the race took some six months, though in 1993 the Progressive Conservatives elected Kim Campbell in a contest lasting about three months.