French presidential candidate Francois Fillon urges supporters to fight on

His wife said on Saturday that she did carry out parliamentary work for him.

With some members of his party urging him to drop out, Sunday's rally on the Trocadero plaza opposite the Eiffel Tower - heavy rain is forecast - will be a test of how much confidence remains.

Once the frontrunner, Fillon is mired in a scandal over his wife's pay, and his campaign has been in serious trouble since he learned last week that he could be placed under formal investigation for misuse of public funds.

Protesters plan two counter-demonstrations in Paris during his rally.

Penelope Fillon said she agreed to the interview to "put an end to the insane rumors", including that the couple might be headed for divorce or that she had been hospitalized.

"At the beginning of this story, I thought I had to explain myself first to the police", Penelope Fillon, who was born in Wales, told Le JDD, adding, "I was so taken aback by violence and hysteria that I shut myself up in my Welsh shell". Fillon's campaign chief and main spokesman quit on Friday and the centre-right party UDI withdrew its support.

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.

Polls now show he could be eliminated in the first round of the two-stage contest on April 23, leaving Le Pen and Macron to contest the May 7 runoff.

Ahead of a rally to support him in Paris on Sunday, Fillon appeared defiant.

Over the next couple of days Fillon's fate will likely be resolved.

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 called on Mr Fillon to cancel the event.

French lawmakers are allowed to employ family members, but investigators are searching for evidence of what work she did. The Fillons insist they did. Fillon faces corruption charges.

Juppe has said he would only replace Fillon if the candidate makes the decision to pull out himself.

Many spoke of the need to defend Fillon's programme suggesting his plan for France was more important to them than the allegations he had helped his wife earn hundreds of thousands of euros for a "fake job" as a parliamentary assistant.

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

  • Arturo Norris