PARIS - For more than two hours, France's presidential front-runner needled his challenger during a debate Wednesday -- a little sarcasm here, a comment about her partner there -- all wrapped in a veneer of chivalry and always addressing her as "Madame."

Finally, Segolene Royal snapped. The woman seeking to become France's first female president erupted in anger toward the end of the prime-time duel with conservative Nicolas Sarkozy.

It was surprising -- and potentially damaging -- that Royal, not Sarkozy, proved quick to anger. During their bitter election campaign, the Socialist has sought to portray her conservative rival as too unstable, too brutal, to lead the nuclear-armed nation.

In front of millions of television viewers, Sarkozy turned the tables. Royal got furious when he started talking about handicapped children, saying he was "playing" with the issue. "I am very angry," she said.

"You become unhinged very easily, Madame," said Sarkozy. "To be president of the republic, one must be calm. ... I don't know why Mrs. Royal, who's usually calm, has lost her calm."

On policy, the first and last debate between the two candidates before Sunday's runoff election produced no major surprises. They disagreed on how to get France's sluggish economy working again, on whether Turkey should join the European Union, on how to safeguard French pensions and on whether taxes should be cut.

Royal, who is behind in polls and needed to score points, immediately went on the offensive, criticizing Sarkozy's record as a minister in President Jacques Chirac's government before he became a candidate for the presidency.

Sarkozy, leading in the polls and looking to get through the debate unscathed, did not rise to Royal's baiting, even after she repeatedly interrupted him.

"Will you let me finish?" he asked at one point.

"No," said Royal.

"Ah," replied Sarkozy.

An immediate point of contention was France's 35-hour work week -- a landmark reform for Socialists, but decried by business leaders as a crippling brake on companies.

Sarkozy wants to get around the 35-hour week by making overtime tax-free to encourage people to work more. He described the shortened work week as a "monumental error," and noted that no other country in Europe had followed France's lead.

Royal defended the 35-hour work week as a form of social progress and asked why, if it was so opposed, the government in which Sarkozy served had not gotten rid of the legislation. Repeatedly, she accused Sarkozy -- who served as the interior and finance minister -- of having failed to improve France while he was in government.

"What did you do for five years? Because for five years, you had all the power. There's a credibility problem," she said.

He, in turn, suggested that her economic program was unworkable and lacked precision. And he dug at her partner and the father of their four children, Socialist Party boss Francois Hollande.

"I know that Francois Hollande said he doesn't like the rich, which is a strange thing," said Sarkozy, adding Hollande "must not like himself."

The debate was expected to draw 20 million viewers or more in a nation re-energized by its hunger for change after 12 lackluster years under Chirac.

Sarkozy and Royal were the last two candidates standing after the April 22 first round of voting in which Sarkozy won 31.2 per cent and Royal had 25.9 per cent, with 10 rival candidates across the political spectrum knocked out of the race.

Royal's underdog bid had gathered some momentum recently.

She outdid Sarkozy on Tuesday with a larger rally in Paris than one he had over the weekend. Also Tuesday, far-right nationalist Jean-Marie Le Pen, who placed fourth with nearly 4 million votes, urged his supporters to abstain Sunday. Polls show his voters were more likely to back Sarkozy than Royal, and it could cut into Sarkozy's support if they stay home.

Sarkozy, who built much of his campaign on a pledge to break with the Chirac era, promised in his concluding remarks not to disappoint or betray the French if they elect him. Royal urged voters to be "daring" enough to elect a woman, citing the example of German Chancellor Angela Merkel.

"I know that for some ... it is not easy to tell oneself that a woman can shoulder the highest responsibilities," she said. "Others do it elsewhere in the world."