Serge Cardin, who is running against Liberal Leader Jean Charest in the Sherbrooke riding, said Marois' gender could thwart her ambitions of becoming premier.
The former Bloc Quebecois MP said some people might not be ready for a woman premier.
He told the Cogeco radio network he is ''greatly disappointed'' by such an attitude.
Marois said later that Cardin's comments were misinterpreted.
''I am persuaded that Quebecers are altogether ready to accept the political leadership of a woman," she said on the hustings.
As for Cardin, he issued a statement to say his remarks did not properly reflect his thoughts on the matter.
He called Marois ''the most competent (leader) to be premier — and that has absolutely nothing to do with the fact she's a woman.''
Charest also chipped in on the debate, saying he can't believe ''for one second that people still vote in terms of a candidate's gender.''
Cardin's comments echoed those of Claude Pinard, who said last November that a significant portion of the electorate wouldn't vote for Marois because she is a woman.
Pinard, a PQ member of the national assembly at the time, is not seeking re-election.
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