Centrist Emmanuel Macron solidified his status as frontrunner in France's presidential election on Monday in a televised debate during which he clashed on immigration and Europe with his main rival, far-right leader Marine Le Pen.

A snap opinion poll showed Macron, a former economy minister who has never run for public office before, was seen as the most convincing among the top five contenders in a marathon debate of nearly three and a half hours that delivered no knock-outs.

The debate, and the two others that will follow ahead of the April 23 first round, are seen as key in an election in which nearly 40 percent of voters say they are not sure who to back.

Macron clashed with Le Pen when she talked about a rise of radicalism in France and said he was in favor of the burkini, a full-body swimsuit worn by some Muslim women that stirred much controversy in France last summer.

Opinion polls have for weeks shown Le Pen and Macron, an independent centrist who used to be Socialist President Francois Hollande’s economy minister, pulling away from the pack in an election full of twists and turns which is taking place against a backdrop of high unemployment and sluggish growth.

Twenty-nine percent of viewers thought Macron was the most convincing, ahead of firebrand leftist Jean-Luc Melenchon with 20 percent, while Le Pen and conservative Francois Fillon were tied in third place, a snap survey conducted online by Elabe pollsters towards the end of the debate showed. Socialist candidate Benoit Hamon came in last.