An apparent threat by far-right leader Marine le Pen to punish state employees who "persecute" political opponents may have eroded her support, according to a poll which found her first-round lead in France's presidential election slipping.
But French prosecutors requested a waiver a year ago after she tweeted three images of Islamic State executions, including.
Fillon has issued a half-hearted apology for employing his wife and two of his children as parliamentary assistants over a number of years for which they earned a combined total of nearly one million euros.
Polls now show however that Le Pen will be beaten in the runoff by either the fast-rising Macron or the conservative candidate.
Mr Haski described Fillon's and Le Pen's supporters as being "in very different positions", adding that allegations surrounding the Front National leader's misuse of European Union funds are "not affecting her at all".
The odds are improving that Marine Le Pen will become the next president of France.
Fillon, who has denied wrongdoing from the start over allegations his wife was paid for work she may not have done, nevertheless stepped up those attacks.
Fillon is also experiencing internal setbacks to his campaign, as his European and worldwide affairs representative Bruno Le Maire announced Wednesday that he was resigning. A host of polls show the National Front candidate winning the first of France's two-tiered presidential election.
In that second round, he is now projected to face Marine Le Pen, the far-right leader with an anti-immigration, anti-EU platform.
Le Pen is also accused of using the funds to pay her bodyguard 41,554 euros for the October- December 2011 period, Xinhua news agency reported.
Fillon will meet investigating magistrates on March 15 but he made a defiant statement, saying the charges were "entirely calculated to stop me being a candidate for the presidential election".
On Wednesday, influent members from his Republicans party called on him to renounce.
He's due to be placed under formal investigation just 48 hours before the deadline to confirm France's presidential candidates.
Le Pen - whose candidacy has not suffered from her legal woes - dismissed the investigation as "political maneuvering". Macron, a 39-year-old who has never held elected office, is presenting himself as a fresh face without political baggage.
"Everywhere, from Donald Trump's America, to Narendra Modi's India, from Xi Jinping's China to Theresa May's United Kingdom, economic patriotism is prevailing", she said.
This week, Mr Fillon announced that he will be summoned for questioning over the allegations known as "Penelopegate" in the next couple of weeks.
Current polls suggest Macron and Le Pen have the best chances of finishing on top in the first round vote, followed by Fillon, and that Macron would easily win the runoff.