French presidential candidate Marine Le Pen’s success in the first round of elections was widely attributed to her hard-fought effort to “detoxify” her far-right National Front party of the anti-Semitism that marked its past, and to root out Holocaust minimizers from its leadership. There was even a French word coined for the effort, dédiabolisation — literally, “undemonization.”

But demons are hard to suppress: It turns out the politician Le Pen picked to run the party while she focuses on the election reportedly previously stated that he isn’t convinced the Nazis could have used poison gas Zyklon B to murder Jews in extermination camps, and insisted there’s a difference between denying the Holocaust and merely “posing ... a certain number of questions” about “chemical use for example.”

Jean-François Jalkh, now the National Front’s interim president, was the party’s vice president. A lifelong FN member, he joined the party in 1974 when he was just 17 years old. Before today, he was largely unknown, even to most French voters — a party official quietly working in the background while the Le Pen family took the national (and international) spotlight.

But a little sleuthing by the French press, first by a journalist named Laurent de Boissieu and followed up by the French daily newspaper Le Monde, has now drawn attention away from Le Pen and turned eyes squarely on Jalkh.

It’s attention Le Pen would surely like to disappear.

The internet has a long memory

Back in 2000, Jalkh got chatty with an academic named Magali Boumaza. In a wide-ranging interview, he apparently revealed his belief that, from a “technical standpoint,” it is “impossible” that Zyklon B had been used by the Nazis to murder Jews in World War II:

I consider that from a technical standpoint it is impossible – and I stress, impossible – to use it in mass exterminations. Why? Because you need several days to decontaminate a space … where Zyklon B has been used.

Le Monde noted that in the interview, Jalkh, spoke, apparently approvingly, of the “rigor” of some of the now-disgraced former professor Robert Faurisson’s work on the Holocaust. But Faurisson is a known Holocaust revisionist who was prosecuted in 1993 after writing an article denying that Auschwitz was an extermination camp and was later charged with “complicity in contesting the existence of a crime against humanity,” over other comments he made questioning the Holocaust, for which he received a suspended sentence and a fine. (He is widely praised by Holocaust revisionist websites.)

At the time, Jalkh told the interviewer that his own questioning of the details of the Holocaust was not out of “deliberate will to harm anyone,” and explained that on things like Zyklon B, “I believe we should be able to discuss this issue.”

Such questioning, though, is a hallmark of Holocaust revisionists — what scholar Deborah Lipstadt refers to as “soft-core” Holocaust denialism. As Lipstadt wrote in the Atlantic earlier this year, such denialism “does not deny the facts, but it minimizes them.”

Jalkh has denied the quotes being attributed to him. Contacted by Le Monde on Thursday, he said, “This is the first time I’ve heard this...bullshit. I have no memory of it.”

Party members said today Jalkh had filed an official complaint to contest the story.

But BuzzFeed France contacted Boumaza today. She stood by the interview and said she had recorded the conversation.

This could hurt Le Pen’s chances of winning the presidency

Le Pen has tried to rebrand her party by focusing on things like French identity and fears of globalization, while firmly rejecting the party’s anti-Semitic past. Her most dramatic move came in 2015, when she very publicly broke with her father, Jean-Marie Le Pen, the founder of the National Front, who has spent the past few decades calling the Nazi gas chambers a mere “detail of history.”

Yet these new revelations may do serious damage to her attempts at rebranding. Xavier Bertrand, the regional president of Hauts-de-France (a Northern industrial and working-class region of France that voted strongly for Le Pen last week), tweeted on Thursday that “the nomination of Jalkh shows the hideous face of the party. How can anyone abstain in the second round of the presidential [election]?”

La nomination de @JFJalkh à la présidence du #FN montre le hideux visage de ce parti. Comment s'abstenir au 2nd tour de la présidentielle ? pic.twitter.com/AanIjbL9ty — Xavier Bertrand (@xavierbertrand) April 25, 2017

The news also comes at a crucial time in the election. A new poll published this morning reflecting opinion before this story broke showed a small slip by Emmanuel Macron, a centrist former banker, and a small gain by Le Pen.

Comment le mur se rapproche doucement: en sept jours, -6 points pour Macron, +6 points pour Le Pen. pic.twitter.com/i4nWljgCXB — Luc Peillon (@l_peillon) April 27, 2017

But while most polls have had Macron easily beating Le Pen in the final round, many France watchers think the election is by no means decided.

To beat Macron, Le Pen has been appealing to the voters that cast their lot with Jean-Luc Mélenchon, the far left populist candidate, in round one — and she has her eye on those voters who might otherwise abstain, because they are so disenchanted with the mainstream parties.

But to effectively win over voters beyond the National Front’s traditional base of supporters, she’ll have to convince them that she and her party have broken with the past, especially its history of Holocaust denialism and anti-Semitism.

Appointing a man reported to have expressed skepticism about the facts of the Holocaust isn’t likely to help that effort.

This story is part of a Vox collaboration with the Pulitzer Center on Crisis Reporting about the upcoming French elections.