The CAQ candidate in the riding of Nelligan, in western Montreal, told CBC News that Legault is a federalist — an assertion the party leader denies.
"For my opinion, [he's] a federalist," said Philippe Boileau, himself a former Liberal and an avowed federalist.
Boileau did acknowledge he's not the best person to answer the question.
"When you're asking the question to Mr. Legault, what's he answering to you?"
The CAQ leader has been asked it several times during the four-week-old Quebec election campaign. He has said he would vote No in an independence referendum, if one were called today, but that he would not lead the Canadian unity forces even if he were leader of the opposition to a separatist government.
He was also a Parti Québécois cabinet minister for five years and an MNA in the party's caucus until 2009, and has only committed to not holding a referendum on Quebec sovereignty for 10 years.
Asked yet again about his stance on Tuesday evening, Legault responded: "I'm not a federalist, not a separatist. I'm a nationalist. I'm a guy who wants Quebec to stop being in a deadlock. We have to move and all Quebecers have to work together."
Boileau said no one in his largely federalist West Island riding has asked him specifically whether Legault is a federalist, though voters sometimes ask whether Legault supports sovereignty — to which Boileau said he replies "no."