By Sophie Louet
PARIS (Reuters) - French conservative presidential candidate Francois Fillon's shrinking supporter base was eroded further on Thursday, a day after news that he faces a formal investigation for allegations he misused public funds.
A Harris Interactive poll showed 25 percent of people want him to continue as a candidate, down from 35 percent a month ago, while within his Republicans party there were more resignations from his campaign after he decided on Wednesday to stay in the race.
Le Parisien newspaper said Fillon's Paris house was searched on Thursday morning by investigators probing allegations that he paid his wife hundreds of thousands of euros of public money to do very little work. An official at the financial prosecutor's office declined comment.
A defiant Fillon said he would not give in despite suffering what he said were "weeks of attacks with disproportionate violence".
"You have a fighter before you," he told cheering supporters waving French flags at an evening rally in the southern city of Nimes. "...I have no intention of giving in."
Former poll favorite Fillon, who complains of unfair treatment from the justice system and media, says he has done nothing wrong.
With less than two months to go to the April 23 first round vote, surveys now consistently point to a run-off on May 7 between independent candidate Emmanuel Macron and far-right National Front leader Marine Le Pen that Macron would win.
Macron announced a full manifesto on Thursday while Le Pen gave a speech on "intelligent protectionism", calling for the nationalization of France's public debt.
"Everywhere, from Donald Trump's America, to Narendra Modi's India, from Xi Jinping's China to Theresa May's United Kingdom, economic patriotism is prevailing," she said.
One of the first opinion polls partly taken after Fillon's legal woes deepened on Wednesday, when adviser Bruno Le Maire quit his campaign, showed his support dipping below 20 percent for the first time in a week and the gap widening between him and the two leaders.
The Elabe poll, carried out between Tuesday and Thursday, showed Fillon on 19 percent, trailing Le Pen on 27 percent and Macron on 24 percent.
On Thursday, campaign treasurer Gilles Boyer, deputy campaign director Sebastien Lecornu and adviser Vincent Le Roux followed Le Maire's lead, along with a number of more junior campaign staff.
Three other high-ranking lawmakers from the left wing of the party - Benoist Apparu, Christophe Bechu and Edouard Philippe - also quit the Fillon cause, saying their decision was prompted by his repeated attacks on the judiciary.
The 62-year-old ex-prime minister is due to be questioned on March 15 by investigating magistrates, who will decide whether to place him under formal investigation. Supporters plan a rally in Paris on Sunday backing his campaign and protesting at his treatment.
Sources in the Fillon camp have said there was a strong push by some in the party on Wednesday to have former prime minister Alain Juppe stand in Fillon's place, but that the plan was vetoed by Nicolas Sarkozy, the former president.
"I am convinced that Francois Fillon is about to fall," Georges Fenech, a lawmaker who led a failed rebellion against Fillon last month, told France Info radio. "It seems to me that today only he (Juppe), with all his experience, can carry the flame."
Juppe, 71, has insisted he has no interest in replacing Fillon.
(Reporting by Sophie Louet; Writing by Andrew Callus and Adrian Croft; editing by Mark John and John Stonestreet)