Embattled presidential candidate faces elimination in French election
The 62-year-old was chosen in a hard-fought primary as champion of the conservative party, the Republicans.
Only 19 percent of those questioned said they would vote for the former premier, a fall of about six points over the last month, Les Echos newspaper, which commissioned the poll with Radio Classique, said.
Far-right leader Marine Le Pen, with around 26 percent of the vote, and former economy minister Emmanuel Macron, with around 22 percent, would go through to the runoff, it said.
The survey is based on intentions for the first round of voting, due on April 23, and on the assumption that centrist leader Francois Bayrou is in the race.
Twenty percent said they would vote for Fillon if Bayrou, who has yet to announce whether he will stand, did not run.
If no candidate wins an overall majority, a runoff between the two frontrunners will be held on May 7.
The survey found Macron would trounce Le Pen in the second round with 65 percent of the vote against a paltry 35 percent for her.
The poll was conducted among 1,053 people on Monday and Tuesday, just before an explosive new report by Le Canard Enchaine weekly which said around one million euros ($1.1 million) was paid to Fillon's wife, Penelope, and his children, who were separately employed as parliamentary aides.
Fillon, 62, was chosen in a hard-fought primary as champion of the conservative party, the Republicans.
Fillon has denied any wrongdoing but his status as frontrunner has been badly hit by the scandal.
During the primary, he stressed his reputation for probity, attacking his former boss and presidential rival Nicolas Sarkozy who was embroiled in a slew of scandals.
One beneficiary of the uproar is Macron, 39, a fast-rising centrist and former minister under the Socialists.
He is a telegenic fresh face in French politics but criticised by some as lacking substance.
JOIN OUR PULSE COMMUNITY!
Eyewitness? Submit your stories now via social or: