Eric Caire, one of just a handful of Action democratique du Quebec members of the national assembly, has become the first person to enter the party's leadership race.
Caire, 43, was first elected to the legislature in 2007 and retained the seat in last December's election.
ADQ officials announced Monday that hopefuls have until Sept. 22 to declare their candidacy.
All party members will have the right to vote and the new leader will be announced next Feb. 7.
Mario Dumont stepped down earlier this month after the party won only seven out of 125 seats in December.
Sylvie Roy will remain interim leader.
