The two candidates in this weekend's presidential election face off Wednesday in their only televised debate, the last best chance for Socialist Segolene Royal to make up ground on conservative front-runner Nicolas Sarkozy. Some estimates said the live debate could draw more than 20 million viewers. The carefully choreographed duel will be a challenge to both contenders, the last two standing after the April 22 first round. In that vote, Sarkozy won 31.2 percent and Royal had 25.9 percent, with the remainder spread among 10 rival candidates across the political spectrum. Royal's bid has gathered some recent momentum. She outdid Sarkozy on Tuesday with a larger Paris rally than one he had over the weekend. Also Tuesday, far-right nationalist Jean-Marie Le Pen, who placed fourth, 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 Le Pen's voters stay home. The challenge for Sarkozy in the debate, many say, will be not to appear too macho against Royal, the first woman with a clear shot at the presidency, but also not to use kid gloves against her. Royal, on the other hand, may need to come out on the offensive, to try to trip Sarkozy up. Socialist Party leader Francois Hollande said Sarkozy is going to try to simply get through the matchup unscathed. He "is going to be playing for time, and playing for a 0-0 draw." Hollande said on Canal Plus TV. Sarkozy, who has held a lead in the polls since January, sought to tamp down speculation that the showdown could be decisive. "I don't think the French choose a president on the lone impression that they'll have after a two-hour debate," he told France-Inter radio Wednesday. The last head-to-head presidential-race debate, pitting Jacques Chirac against Socialist Lionel Jospin in 1995, drew 17 million viewers. Chirac won the first of his two terms that year. In 2002, he refused to debate Le Pen, who stunned much of France by ousting Jospin and other contenders in the first round.