As supporters of Marine Le Pen search for reasons why their candidate got a lower-than-expected score, one point comes up repeatedly -- the debate.

In the debate Wednesday night, Marine Le Pen went on the offensive from the start, launching personal attacks on Emmanuel Macron and barely talking about a program she'd spent years constructing. Mr. Macron parried in the debate, pointing to what he said were gaping holes and inconsistencies in her program.

“We didn’t explain our program enough," said Aymeric Mahiet, a 27 year-old Le Pen supporter at the election-night party here. “It was perhaps the image of the party that let us down.”

Key among the concerns of supporters is Ms. Le Pen's hard-line stance on quitting the euro. During the debate, Mr. Macron highlighted the National Front leader's changing position on how she would exit the currency.

“I am convinced people were scared because of that. It wasn’t always well explained, notably during the debate,” said Damien Medel, a 28-year-old supporter of Ms. Le Pen.