Some 9.8 million viewers tuned in to Monday night's French presidential debate, according to one of the television channels that broadcast it.
The debate reached 47.9 per cent of the country's television audience, broadcaster LCI said, citing audience measurement agency Mediametrie.
The debate saw heated exchanges between far-right candidate Marine Le Pen and her centrist and leftist rivals on issues such as immigration, law and order, and secularism and Islam.
Centrist former economy minister Emmanuel Macron appeared the clear winner of the debate, despite his lack of electoral experience, according to a snap poll for broadcaster BFMTV afterwards.
Opinion polls on voting intentions suggest Macron is likely to come second behind Le Pen in April's first round of voting and is favoured to beat her in the decisive run-off vote on May 7.
Some 29 per cent of viewers polled found Macron the most convincing candidate, with radical leftist Jean-Luc Melenchon, conservative Francois Fillon and Le Pen bunched together on 19 to 20 per cent.
Socialist candidate Benoit Hamon lagged on 11 per cent. The leftist opponent of Socialist President Francois Hollande has failed to gain momentum in the campaign, with centrist and centre-left voters peeling off to Macron and Melenchon outflanking him on the left.
Macron also came out top when viewers were asked which candidate had the best plan for France and who had the characteristics needed to be president. Former prime minister Fillon came second on both those counts, polling firm Elabe found.
Fillon, stuck in third place in the polls amid allegations he gave his wife a lucrative fake job as his parliamentary assistant, stood aloof from most of the cut and thrust of the debate.
He emphasized his experience and pushed his austerity-based economic programme, while warning that Le Pen's plan to leave the euro would lead France into chaos.