Pierre Karl Péladeau’s abrupt exit as leader of the Parti Québécois launches the sovereignist party on the road to another tumultuous leadership contest – a mere 50 weeks after it held its last one.

The political shock of Mr. Péladeau’s departure had barely abated before potential names began to surface to take over the now-headless party. Whoever becomes the ninth leader of the PQ will have an unforgiving schedule and sizeable task: Helming a party running second in the polls and known for its often fractious internal politics toward a provincial election only two years away.

“This is a tough blow for the party because it’s taking them by surprise. It wasn’t part of the agenda,” said Louis Massicotte, a political scientist at Université Laval in Quebec City. “It’s like a slap in the face. Mr. Péladeau is leaving them suddenly, abandoning his post.”

The departure marks the end of an awkward political relationship between the media tycoon and a traditionally centre-left party, which had yet to see him deliver on the PQ’s hopes of redemption. The PQ, after a rout in the 2014 election, is still trailing in support despite missteps by the ruling Liberals.

“The only good for the PQ is that it can find a leader who is probably going to be better than he was,” Prof. Massicotte said. “He really didn’t have it. This man was seen as a saviour and he didn’t perform. The party had big hopes for him, and now it sees he wasn’t up to the task. He didn’t even make it to an election.”

Names being floated to replace Pierre Karl Péladeau include:

Jean-Martin Aussant, 45, an economist who quit the PQ in 2011 to form a rival sovereigntist party. A former vice-president of Morgan Stanley Capital International, he recently returned to Quebec from London and is viewed as the political protégé of late premier Jacques Parizeau. Mr. Aussant is seen as an impatient sovereigntist, quitting the PQ because he felt it didn’t promote the option forcefully enough.

MNA Alexandre Cloutier, 38, the (distant) second-place finisher behind Mr. Péladeau in last year’s PQ leadership race. A onetime Supreme Court clerk who studied international law at the University of Cambridge, Mr. Cloutier is a constitutional lawyer and up-and-comer who represents generational change in the PQ.

MNA Véronique Hivon, 46, also a rising star, who made a name for herself by rallying non-partisan support for Quebec’s trailblazing legislation on medically assisted death.

MNA Jean-François Lisée, 58, a former adviser to two PQ premiers. He put a distance between himself and Mr. Péladeau during the last leadership race, which could hold him in good stead going forward. After dropping out of the contest, Mr. Lisée sounded resigned and said his party wanted to have “its Pierre Karl Péladeau moment.” However, Mr. Lisée polled dead last among the main rivals the last time around and failed to pick up any endorsements from his PQ caucus colleagues.

MNA Bernard Drainville, 52, who rallied to Mr. Péladeau after his own failed leadership bid last year. The opposition House Leader insisted only four months ago that Mr. Péladeau would be leading the party through to the next election. “Pierre Karl Péladeau is not a quitter,” he said. Mr. Drainville has offered the PQ strong bench strength in the legislature, but his star is tainted by having been the main pitchman for the PQ’s derided Charter of Values.

No sovereigntist-party leadership race is complete without speculation about stalwart Gilles Duceppe, 68. He has been touted as a potential leader for the PQ in the past, and he very briefly put his name in the running in 2007. However, Mr. Duceppe’s currency has been in decline since a comeback bid in last year’s federal vote failed to stop the Bloc Québécois’ drop in popular support, and he didn’t win his seat in Montreal. He resigned as leader.

Members of the PQ caucus are to expected meet by the end of the week to choose an interim leader.