By Sophie Louet and John Irish
PARIS (Reuters) - Embattled French presidential candidate Francois Fillon was under growing pressure to quit the race on Saturday as his party leaders brought forward a meeting to discuss the situation and former allies shied away from a planned rally to support him.
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 this week that he could be placed under formal investigation for misuse of public funds.
After a string of resignations among advisers and backers, the 63-year old former conservative prime minister is banking on a rally of supporters in Paris on Sunday to show his detractors that he remains their best hope to win the presidency.
But as soon as he ended a campaign meeting on Saturday at which he defended his political plans as the only credible future for the country, The Republicans party announced it was moving up a meeting of senior officials to discuss the latest developments by 24 hours to Monday.
"Given the evolution of the political situation just seven weeks from the presidential election ... the political committee, has been brought forward," it said in a statement.
Former prime minister Alain Juppe, who lost to Fillon in the November primary and has been widely touted to replace him should he step aside, is not attending.
Opinion polls continue to show Fillon would fail to make the second round of the April/May election. Instead, centrist Emmanuel Macron is consolidating his position as favourite to win a second-round head-to-head against far-right National Front candidate Marine Le Pen.
Fillon's backers have been on the offensive since the candidate revealed that he could be placed under formal investigation. They are hoping to get some 45,000 people at a rally in central Paris on Sunday to show he still carries favour among grassroots supporters.
But an Ifop poll of 1,002 people published on Saturday showed 71 percent of French voters want him to quit the race, up six points from an identical survey on Feb. 19.
It also showed support from within Republican voters falling to 53 percent from 70 percent two weeks ago.
At Saturday's campaign meeting he remained defiant.
"Brick by brick, I have prepared an ambitious programme, the only one in my eyes that can restore France's vitality," he told a smaller-than-expected crowd of supporters north of Paris.
"I am being attacked, but through me what they are trying to attack is the national recovery and a will to change that you all want. Don't abdicate! Don't give up!" he said.
Fillon suffered more blows on Friday when his campaign chief Patrick Stefanini and chief spokesman Thierry Solere both quit and the centre-right party UDI withdrew its support.
On Saturday, five Republican party members of the European Parliament joined the exodus, calling for a new candidate to represent them.
A poll published on Friday may also have rattled the Fillon camp. It showed that if he were to step down and be replaced by Juppe, then Juppe would make it to the run-off and eliminate Le Pen in the process.
"The pilot is in the cockpit, the door is locked so it's difficult to talk with him, but we don't want the plane to crash," Jean-Baptiste Lemoyne, a senator from Fillon's party told LCI television.
Fillon has denied any wrongdoing and complained of judicial and media bias that amounted to a "political assassination". His attack on the judiciary in particular has caused unease within his party.
Sunday's planned demonstration has also worried some within right-wing ranks over fears that it will be hijacked by hardline conservative movements. Several heavyweight party officials said on Twitter they would not attend.
"It's making me uncomfortable," said Christian Estrosi, the right-wing president of France's southeastern region. "This rally also seems to want to defy the institutions of our country, and that's not possible."
(Additional reporting by Elizabeth Pineau; Editing by Hugh Lawson and Mary Milliken)