PARIS -- France's presidential campaign is facing a potential turning point as conservative candidate Francois Fillon, facing corruption charges, holds a rally Sunday that could determine whether he stays in the race.

The rally across from the Eiffel Tower is meant to gauge Fillon's remaining support after numerous defections by conservative allies just seven weeks before the first round of the April-May election. They're disillusioned by how he has handled the investigation into allegations he arranged parliamentary jobs for his wife and children that they never performed.

Protesters plan two counter-demonstrations in Paris during his rally. Fillon is expected to speak on national television Sunday night, though cancelled a radio interview scheduled Monday morning. Fillon's party, The Republicans, is holding a meeting of its political committee on Monday evening to evaluate the situation after Sunday's rally.

Fillon's wife Penelope urged her husband to stay in the race, in her first interview since the scandal broke in January.

"Unlike the others, I will not abandon him," Penelope Fillon was quoted as saying in the Journal du dimanche newspaper.

"I told him to continue to the end. Every day I told him that," she said, but added, "He is the one who will decide."

If Fillon quits, that would throw France's already exceptional, unpredictable campaign into disarray anew.

Many conservatives want Alain Juppe to run in his place for the two-round April-May vote, though their Republicans party has no official Plan B. Juppe, who campaigned on a more moderate platform than the tough-on-security, pro-free market Fillon, was runner-up in the conservative primary.

Fillon was once the front-runner in the race, but his ratings have fallen since the jobs allegations were revealed by weekly Le Canard Enchaine.

Polls now suggest far-right leader Marine Le Pen and centrist Emmanuel Macron would come out on top in first round vote April 23, and face off in the May 7 runoff.

Fillon called Saturday on supporters not to "abdicate" to those trying to destroy him and vowed to remake France. His campaign director and campaign spokesman were among those deserting the Fillon team in recent days.

A group linked to an ultraconservative political movement, Common Sense, has associated itself with Sunday's rally, and is reportedly organizing buses from around the country to bolster support.

Paris Mayor Anne Hidalgo tweeted that the event "endangers" French values, claiming its real goal is to demonstrate against investigative judges, police and journalists "bringing to light the truth."

Financial prosecutors are investigating reports that Fillon's wife and two of their five children earned more than 1 million euros in taxpayer-funded jobs as parliamentary aides that they never carried out. It is legal in France to hire relatives for public jobs, if they actually work. The Fillons insist they did.

Fillon initially said that he would step down if charged, but decided Wednesday to maintain his candidacy even though he's been summoned to face charges on March 15.

Penelope Fillon said in the Journal du dimanche interview that the parliamentary jobs were real, though low-profile. An extremely discreet political spouse, she described living through horror as the allegations exposed her family's private lives and prompted outrage and disappointment, especially among followers who had seen Fillons as models of political and moral rectitude.

"It's really the opposite of what I think I am. I felt like I passed through lightning. It is the worst thing I have lived through in my life," Penelope Fillon is quoted as saying.

The scandal has highlighted entrenched corruption in French politics.

Juppe, seen as the potential saviour of conservative chances at the presidency, was convicted in 2004 for an illegal party funding scheme and barred from elected office for a year.

Meanwhile, candidate Le Pen is at the centre of several judicial inquiries along with her anti-immigration National Front party.

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Elaine Ganley contributed to this report.