French presidential candidates Nicolas Sarkozy and Francois Hollande are preparing for their one and only face-to-face televised debate on Wednesday evening, in an event that is of crucial importance to the incumbent’s hope for retaining his power.

With Sarkozy behind the Socialist front-runner Hollande by up to seven percentage points in the latest opinion polls, Sarkozy will have to deliver a knock-out blow in the debate, just ahead of Sunday’s decisive second-round vote.

Sarkozy suffered a setback on Tuesday when the head of the extreme right-wing National Front party, Marine Le Pen, who gained an unprecedented 18 percent of the vote in the first round of the election, declined to endorse either candidate and declared she will cast a blank ballot in protest.

Le Pen’s refusal to support Sarkozy may lead many of her supporters to similarly boycott the election, which would likely hand a victory over to Hollande.

Sarkozy has tried to co-opt Le Pen’s anti-immigration message since the very start of the campaign. Hollande himself has mildly tried to court the far right vote as well, telling reporters that France has too many “illegal immigrants,” a slight variation of Sarkozy’s earlier declaration that the country has “too many immigrants.”

The BBC reported that, while this may be Sarkozy’s last chance to save his political career, he has an advantage in terms of his charismatic debating skills.

He may also attack the mild-mannered Hollande for having never held a senior office in government.

Christopher Bickerton, an associate professor of international relations at the Sciences Po University, told Reuters, Sarkozy is very combative, very pugnacious. He can be quite hard with his interlocutors and Hollande has to avoid being seen to be browbeaten.

Moreover, given the prominence of France’s fragile economy and high debt as key topics of the campaign, Sarkozy is likely to hammer Hollande for opposing austerity measures and spending cuts.

On Tuesday, at a May Day rally, Sarkozy made a plea to trade unions who are expected to widely support Hollande, by declaring, Put down the red flag and serve France!

From the other side of the aisle, Hollande will likely blame Sarkozy’s policies for creating rampant unemployment -- now at about 10 percent -- and for France losing its AAA credit rating.

At a campaign rally outside France, Hollande defended the unions and criticized Sarkozy’s failure to create jobs.

When there are four million unemployed, when joblessness has increased by more than a million, who defends the value of work and who is ruining it? he asked.

Among other measures, Hollande has proposed the creation of 60,000 jobs for teachers and pushing the minimum retirement age back to 60 from 62.

Gavin Hewitt, BBC’s Europe Editor, said, “These debates rarely rescue a failing campaign but they have the potential to surprise, to deliver a defining moment.”

About one-third of France's 63 million citizens are expected to watch the 2 1/2 hour debate, which will begin at 9 p.m. Paris time.