French far-right presidential candidate Marine Le Pen is painting herself as David against rival Emmanuel Macron's Goliath as she tries to overcome a poll gap and broaden her support base ahead of a May 7 runoff.
In comments unearthed by a journalist at La Croix newspaper and republished in Le Monde, Jalkh, an MEP, argued he was not a Holocaust denier but had spoken to a chemistry expert about Zyklon B, which was used in the extermination chambers.
Zidane, who was born in Marseille and comes from Algerian descent, took a similar stance when Jean-Marie Le Pen - Ms Le Pen's father - made it to the second round of the 2002 presidential election.
Jalkh was to continue in his position as Secretary-General of the Jeanne micro-party, founded by Le Pen, for which he was now being investigated amid allegations that the party misused public funds during the 2012 legislative elections.
Le Pen stole a march on Macron on Wednesday by making an unannounced visit to a Whirlpool factory in northern France where the United States appliances giant is threatening to partially outsource production to Poland.
Anti-Semitism has been a tough subject for Le Pen in the past.
At issue are comments attributed to Jalkh in a conversation with a researcher in 2005 about the work of a professor convicted a couple of times for questioning the scale of Jewish extermination in Nazi gas chambers during World War Two. He wasn't ashamed to say those things just 17 years ago, but now he says he can't remember ever saying them.
Le Pen's decision to step down in favor of Jean-François Jalkh shows that the National Front is still what it has always been - a party for Holocaust deniers, Nazi sympathizers and people who are nostalgic for the Vichy regime.
The National Front will now be led by interim President Steeve Briois, a mayor of the northern city of Henin-Beaumont.
Front member Louis Aliot, Marine Le Pen's partner in private life who announced the move, told BFM TV: "He (Jalkh) wants to defend himself and he will be filing a legal complaint because he feels his honor has been attacked, and I can tell you he firmly and formally contests what he is accused of".
"No, the National Front is not a party like any other", Macron said in the town of Chatellerault.
But in a couple of potential blows to the centrist favourite, defeated far-left leader Jean-Luc Melenchon stopped short of endorsing him, despite telling his faithful not to vote for Le Pen.
"I think we should be able to discuss this problem", Jalkh said at the time.
National Front's founder, Jean-Marie Le Pen, has several convictions for denying aspects of the Holocaust, as well as for inciting racial hatred against Jews.