Evan Solomon: What to expect in tonight’s debate

What should you watch for during this next phase of Campaign 2015?

Tonight’s French-language debate is critical for NDP Leader Tom Mulcair, who has been shedding numbers in Quebec like a sheepdog in summer. He needs to re-establish the ballot-box question in Quebec as “change.”

In an act of political jiujitsu, Conservative Leader Stephen Harper has turned the question from “change” to “niqabs.” While it is working for Harper politically in Quebec, it has unleashed the wild winds of identity politics.

Of course, in Quebec, there are other, equally divisive litmus tests on protecting women’s rights. One is abortion. Will it get unleashed during tonight’s debate?

Finally, the Trans-Pacific Partnership (TPP) is in the spotlight. For Harper, a big trade deal is a win, despite the blowback from farmers and auto unions. Liberal Leader Justing Trudeau can skate here, supporting the deal while demanding to see the details. For Mulcair, it is the most difficult. He has run a campaign as the “the real alternative,” a safe, balanced budget by an NDP that is ready to govern pragmatically. Can he afford to look as though he opposes a major trade deal, even if he has legitimate concerns? Or does he tack again toward the middle and lose the progressive-left voters he needs so badly? For him, the timing of this deal could not be worse.

Tonight’s debate will be the most volatile yet.