PARIS — Francois Fillon on Monday defiantly refused to drop out of the race to be France’s next president despite an investigation into whether well-paid political jobs he gave his wife, son, and daughter were genuine.
The scandal has knocked Fillon from his perch as favorite in the April-May voting.
The conservative politician who served as prime minister from 2007 to 2012, the chief workhorse under then-President Nicolas Sarkozy, has long had a reputation as low-key, reliable, and standing for moral rectitude, making the corruption scandal particularly shocking to his party, supporters, and the French as a whole.
On Monday, two weeks after revelations first surfaced, he scrambled to save his candidacy.
‘‘I have nothing to hide,’’ Fillon told a news conference aimed at stanching the blood-letting and conspiring within his party about who might replace him as candidate. ‘‘All acts described [in the media] are legal and transparent.’’
Determined despite unending attacks, Fillon, stressing his 32 years in politics, vowed to stay in the race.
‘‘Nothing will turn me from my duty to be a candidate in the presidential election,’’ he said.
Fillon apologized for employing his wife, while noting that it is not illegal and he is not the only politician to have done so.
‘‘What was acceptable yesterday . . . is not today,’’ Fillon said.
‘‘It was a mistake. I deeply regret it, and I present my excuses to the French.’’
French politicians are allowed to hire family members as aides as long as they actually do the jobs for which they are paid.
Prosecutors are trying to determine whether Fillon’s family members did the jobs of parliamentary aides. The preliminary probe involves suspicions of embezzlement and misappropriation of public funds.
As prime minister and in his presidential campaign, Fillon put the accent on cutting back on government spending. A key campaign promise this year is to slash half a million public-sector jobs.
Fillon’s popularity has dropped in the past two weeks following allegations by the Canard Enchaine newspaper that his Welsh-born wife Penelope was paid 830,000 euros ($900,000) over 15 years without doing anything to earn the salary. The Paris prosecutor’s office on Thursday expanded its investigation to include Fillon’s son and daughter.
Some conservative lawmakers have pressed for him to step down to improve the party’s chances of winning the election. The first vote is on April 23, and the top two finishers compete in a runoff on May 7.
If Fillon’s bid to win confidence while wading through a legal investigation fails to work, the election could become an unusual face-off without a strong right, or no right at all.
Fillon reiterated he would withdraw if he were charged — but questioned whether the financial prosecutor’s office handling the case was the proper jurisdiction. A statement by the prosecutor’s office said it was competent.
Officials of the far-right National Front party, including leader Marine Le Pen, also are under investigation for their use of aides in the European parliament.
Fillon laid out for reporters in some detail his own facts about the accusations.
‘‘Yes, I employed my wife as an aide,’’ Fillon said. He said she was paid an average 3,677 euros (almost $4,000) per month over 15 years.
‘‘They call this job fictitious,’’ he said, laying out the ill-defined duties of parliamentary aides who work ‘‘in the shadows.’’
‘‘Her salary was perfectly justified because her work was indispensable to my activities as an elected official,’’ he said.
Fillon and his family live in an elegant manor in the Sarthe region southwest of Paris. To bolster his reputation he detailed the worth of the building — 750,000 euros (about $804,000) — and other holdings, and said he does not have to pay the tax on fortunes demanded of the wealthiest. Fillon said he was publishing his assets online Monday night.
Fillon said the scandal grew out of a political conspiracy to take him out of the race, and make it a face-off between far-right leader Marine Le Pen — whose family he blasted as ‘‘untouchable’’ — and Emmanuel Macron, an untested former banker and Socialist Party maverick whom Fillon called a ‘‘guru.’’