The next two nights could help determine whether the Parti Québécois will be challenged for its front-runner status in the Quebec election campaign.

That's because a unique debate format will place the new Coalition Avenir Québec party at the centre of the political discussion for two nights.

François Legault is about to square off in a pair of one-on-one contests — the first Tuesday night against Liberal Leader Jean Charest, and the final one Wednesday against the current favourite according to polls, the PQ's Pauline Marois.

Rookie leader Legault is a pivotal player in the three-way race.

His level of support is a wildcard factor in a number of riding battles, with his party in a position to play the role of spoiler even in areas where it's not likely to win.

So far, polling seems to suggest a number of Liberal voters have flocked to the new CAQ party. But the PQ base has held up more steadily, creating a vote split that analysts believe could give the pro-independence PQ a comfortable victory with just one-third of the popular vote.

There are two ways for Legault to break that current pattern: He can start stealing votes from the PQ, or he can start losing some back to the Liberals.

Otherwise, if the current poll numbers hold up, the biggest unknown in this election is whether the PQ could win a majority government on Sept. 4, or be held to the minority hinted at by their current polling levels.

Referendum talk

PQ Leader Marois concluded her one-on-one debate with Liberal Premier Jean Charest on Monday. That debate featured a replay of the battles over independence that Legault says he wants to put aside. A former PQ cabinet minister who once called sovereignty an urgent need, Legault now says he would vote against independence and is tired of debating the issue.

The leaders of the two older parties tackled the topic, however, with considerable energy Monday.

Charest accused the PQ of fostering instability, with its talk of independence. He demanded that Marois come clean and tell Quebecers whether she would hold a referendum.

The PQ leader was vague in her answer. There will be a third plebiscite on independence, Marois suggested, whenever the PQ feels it can win.

"A referendum if necessary, at the moment it's necessary," Marois said.

The province is experimenting with an unconventional debate format in the run-up to the Sept. 4 election. Three of the four encounters will see one-on-one contests, rather than all four main party leaders on stage at the same time.

Over the next two nights, under the new debate format, both Marois and Charest will square off in one-on-one encounters against Legault. Marois and Legault, who are former cabinet colleagues, will face off against each other Wednesday.

Legault left the PQ to create his new party, which has no official position on the independence question and promises not to discuss the issue that has dominated Quebec politics since the late 1960s.