Paris - France's presidential candidates traded fresh blows Thursday after one of the fiercest TV debates in the nation's history, with frontrunner Emmanuel Macron holding on to his status as favourite for the weekend's decisive run-off.The centrist Macron and his far-right rival Marine Le Pen clashed repeatedly over terrorism, the economy and Europe in Wednesday's hot-tempered debate watched by 16.5 million people.Le Pen branded the 39-year-old former economy minister and investment banker "the candidate of the elite" while he called her "the high priestess of fear".After the bruising contest, a snap poll by French broadcaster BFMTV found that 63 percent of viewers thought Macron was the "most convincing" of the two, broadly mirroring forecasts for the decisive election on Sunday.Former US president Barack Obama threw his support behind the pro-EU Macron, offering fresh backing for the candidate.Obama said in a video that Macron had stood up for "liberal values" and had "put forward a vision for the important role that France plays in Europe and around the world".The rivals were at each other's throats again on Thursday, with Le Pen defending the aggressive tone of the debate by arguing that she had tried to "lift the veil... on who Mister Macron is" and he again accused her of lying constantly."He presents himself as a new man who emerged from nowhere... when in fact he emerged from (President) Francois Hollande's government," Le Pen said in a TV interview.'Brutal and violent' debateMacron told France Inter radio: "You can't choke off all of the lies but you can kill off some of them."He filed a legal complaint after Le Pen implied during the debate that he had an "offshore account in the Bahamas"."We will not hesitate to prosecute for defamation anyone who repeats this false information," an aide to Macron said.With just two days of campaigning left, Le Pen received a rowdy welcome in the Brittany town of Dol-de-Bretagne, where protesters threw eggs at her entourage, although she was not hit.Macron headed to the southwestern town of Albi to meet supporters.The aggressive and often unruly debate shocked many observers."It is misleading to call that fist fight a debate," an editorial in the right-leaning Figaro newspaper said.Le Monde said it had been "brutal" and "violent from start to finish".Former Socialist prime minister Manuel Valls, who is backing Macron, said Le Pen "showed her true face" in the debate and "it's worrying".Unpredictable campaign The debate was probably Le Pen's last chance to change the dynamics of the race ahead of the final weekend of a long and unpredictable campaign.But the poll by Elabe for BFMTV showing that Macron had convinced 63 percent of viewers compared to 34 percent for Le Pen suggests she did little to win over new support.Macron would win around 60 percent to Le Pen's 40 percent if the vote were held now, surveys suggest.Le Pen tried to portray Macron as being soft on Islamic fundamentalism, playing to the concerns of many of her supporters after a string of terror attacks in France.But Macron was in combative form throughout, repeatedly portraying Le Pen's proposals as simplistic, defeatist or dangerous and targeting her proposals to withdraw France from the euro in particular.The euro policy "was the big nonsense of Marine Le Pen's programme," he said.Le Pen called the euro, shared by 19 countries in the European Union and blamed by some in France for a rise in prices, "the currency of bankers, it's not the people's currency."In the first round of the election on April 23, Marine Le Pen finished second behind Macron with 21.3 percent after softening the FN's image over the past six years -- but without fully removing doubt about the party's core beliefs.She sees her rise as the consequence of growing right-wing nationalism and a backlash against globalisation reflected in the election of Donald Trump in the United States and Britain's shock vote to leave the European Union."I am the candidate of the people of France such as we love it, of the nation that protects jobs, security, our borders," she said.The debate was unlikely to have swayed committed supporters of either candidate, but it could influence the roughly 18 percent of undecided voters and others who were planning to abstain.Many supporters of Communist-backed candidate Jean-Luc Melenchon, who came fourth in the first round, have said they will not vote on Sunday, comparing the final round as a choice between "the plague and cholera".