The Parti Quebecois is reeling after a fourth member walked away from the provincial separatist group on Tuesday.
Jean-Martin Aussant, who represented a rural riding located between Montreal and Quebec City, will now sit in the National Assembly as an independent.
He told reporters he would continue to vote with the PQ on issues related to sovereignty.
One day earlier, three key PQ members abandoned ship. Actor Pierre Curzi; Lisette Lapointe who is married to Jacques Parizeau; and Louise Beaudoin, a longtime and well-respected party member, all walked away and announced they will sit as independents.
Antonia Maioni, a Quebec journalist and political analyst, said the defections are related to questions about leadership, the direction of the party, and a proposed arena for Quebec City.
She said the three departures on Monday dealt a painful blow to the party.
"They are three heavy hitters. Le Devoir referred to them as the three tenors of the party," Maioni told Â鶹´«Ã½ Channel.
She added: "All three of those members would have been automatic members in a PQ cabinet but now they want to sit as independent sovereignties."
Maioni said a number of issues have been simmering within the party in recent weeks. But PQ Leader Pauline Marois' recent support for the Quebec City arena project has crystallized a rebellion among some party members.
Mayor Regis Labeaume has campaigned for months for support for a rink that could host an NHL franchise. The federal Conservatives had flirted with the project, but eventually backed away saying Ottawa wasn't in the business of building arenas.
Quebec Premier Jean Charest has pledged to pay $200 million towards the cost of the facility, while the city chips in a similar amount.
Meanwhile, Lebeaume has a deal with Quebecor to manage the arena but needs the National Assembly to pass the bill before going on summer break on June 10. If that doesn't happen, the NHL won't take the efforts seriously, Lebaume has said.
The law requires unanimous consent in the National Assembly, meaning the pressure is on among PQ members.
"There are many members of the Party Quebecois who don't like how this bill is being rammed through in the last week of the National Assembly," Maioni said.
She said many members of the traditionally social democratic PQ party are wary of the deal, which gives Quebecor 25-year naming rights and management of the facility, as well as protections against unprofitability.
Former premier Bernard Landry told The Canadian Press it feels as though the party is in the midst of an earthquake that could easily become a tsunami.
