Parti Quebecois Leader Bernard Landry stunned his party by quitting after receiving a 76.2 per cent endorsement from it.
He had previously said 76 per cent would be the minimum support required to say on.
But after the vote was announced Saturday evening, Landry said he required more support to remain.
"It breaks my heart to tell you this, but I'm doing it in the national interest,'' he said to delegates at the party's weekend policy convention in Quebec City.
Landry said he still believed in the dream of Quebec sovereignty.
In noting how the sovereignty movement only narrowly lost the 1995 referendum, Landry said, "The next person who leads the sovereigntist troops must be strongly supported without equivocation.''
Squabbling over the party's leadership does nothing to help the sovereignty movement, he added.
Speaking to CTV Newsnet from the convention, CFCF reporter John Grant said cries of "no, no, no!" from shocked delegates greeted Landry's announcement.
Landry explained himself by saying the PQ was in an excellent position to take power and could move from that to a winnable referendum, he said.
"But he can't lead that fight unless he has stronger support," Grant said, otherwise he'll be undermined by rumours.
Noting Landry is 68 years old, "he just said, 'I can't deal with that,'" he said.
Landry replaced Lucien Bouchard as party leader and premier in 2001.
He lost the 2003 Quebec provincial election to Liberal Jean Charest. This was Landry's first official test of confidence since that election.
Almost a decade ago, Bouchard threatened to quit the party leadership after receiving 76.4 per cent support in a 1996 confidence vote.
Bouchard replaced Jacques Parizeau, who was PQ leader during the referendum.
Former PQ cabinet ministers Pauline Marois and Francois Legault -- and possibly Bloq Quebecois Leader Gilles Duceppe – are early frontrunners to replace Landry, Grant said.
"A lot of Pequistes see him in their soup these days as their saviour," he said. "Another saviour from Ottawa."
Commenting to CTV Newsnet before the vote, Grant said: "PQ leaders never feel safe. This is a party of militants, the party of the base, the party of the rank and file.
"They like to think they're in control here, and no leader from Rene Levesque on has ever had an easy time."
If an election were held today, the PQ would be in government tomorrow, he said, noting the low support for Charest's Liberals.