LAVAL, Que. -- Quebec's party leaders were quietly gearing up Saturday for what could be a crucial series of televised debates as the provincial election campaign reached its halfway mark.

A string of four debates beginning Sunday night could be Premier Jean Charest's best chance for a turnaround before the Sept. 4 election.

They also offer a chance for Francois Legault, leader of the Coalition for Quebec's Future, to make his first real impression as head of his new party.

For Parti Quebecois Leader Pauline Marois, the debates represent an opportunity to strengthen her already considerable lead in the polls. Opinion polls have consistently placed the PQ ahead Charest's Liberals and Legault's Coalition.

While the stakes may be high, Charest tried to lower expectations on Saturday. He said he's expecting to face a barrage of criticism from his political opponents.

"For the past four years we have been the target of an extremely negative campaign on the part of our adversaries," Charest said at a news conference in Laval, just outside Montreal.

"Do you think that's suddenly going to change in the debate? I'm under no illusions."

Charest, though, has a history of using debates as an electoral springboard.

In fact, it was after his performance in the 2003 debate when he sprung some surprises on then-PQ leader Bernard Landry that his poll numbers suddenly spiked and he was elected against all expectations.

Three more debates are scheduled for Monday through Wednesday -- featuring one-on-one battles between Charest, Legault, and Marois.

The challenge facing Legault is considerable. The former PQ cabinet minister isn't known for oratory skills and has in the past blurted out policy statements he's later regretted. He also has far less experience than both Marois and Charest in such situations.

Legault and Marois made no major announcements Saturday as they prepared for the debates, while Charest took a break after a morning announcement promising more funding for public transportation.

The debate on Sunday also offers an opportunity for the smaller, social-democratic Quebec Solidaire to raise its profile. Francoise David, the party's co-spokesperson, will take part.