Until now, the former party president has said only that he'd seek a seat in Quebec as soon as possible.
He's declined to be more specific, even when questioned by rival contenders during an all-candidates debate last weekend.
But Topp now tells the CBC he would ask a sitting MP to step aside, clearing the way for a byelection in Quebec that he'd hope would vault him quickly into the Commons.
A longtime backroom strategist, Topp has won endorsements from many party luminaries.
They include former NDP leader Ed Broadbent, former Saskatchewan premiers Roy Romanow and Lorne Calvert and the late Jack Layton's mother, Doris.
But his campaign appears to have stalled as rivals zero in on his lack of experience as an elected politician and the fact he would have no seat in the Commons should he become leader.
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