On the campaign trail in Brittany on Monday, Fillon changed trains to avoid being met by left-wing activists banging kitchenware at a station on his way.
He also cancelled a visit to the port of Saint-Nazaire, home to a major shipyard.
"The more they demonstrate, they more the French people support me," he commented this weekend after about 30 Basque activists greeted him with a similar cacopany in their region, some pelting him with eggs while shouting "Fillon in prison!".
The opinion polls have not so far borne out his claim - the mainstream right candidate has sunk from second to third position below the far right's Marine Le Pen and ex-economy minister Emmanuel Macron, who has started his own centrist movement.
Scandal has stalked Fillon since the revelations that he employed his wife and two of his children as parliamentary assistants, sparking a legal investigation as to whether they actually did any work.
Since then he has been shown to have been given suits worth thousands of euros by Robert Bourgi, a lawyer deeply involved in France's often-criticised dealings with African leaders, and a 27,000-euro watch by a an Italian-Swiss businessman, Pablo Victor Dana.
Spying claims rejected
Fillon's efforts to fight back have not reversed his fortunes.
In fact, they may have made things worse.Last week he claimed that a secret office run by President François Hollande was spying on him and was behind the various allegations, a claim echoed by Le Pen in relation to her own legal difficulties.
Justice Minister Jean-Jacques Urvoas dismissed that accusation as "at best pure speculation and at worst a wish to manipulate reality" on Monday.
"I wouldn't go that far," was the comment of one of Fillon's closest allies, François Baroin, when asked about the candidate's accusation.
Most MPs and activists of Fillon's Republicans party have effectively given up hope of winning the presidential election, according to Le Monde newspaper.
Two former justice ministers - Dominique Perben and Michel Mercier - have declared their support for Macron - and party members only dare distribute leaflets "at night and in the middle of the country", according to one MP.
Many Republicans are now counting on the parliamentary elections that will follow the presidential ones to save their seats, hoping that a victorious Macron will call on them to join the goverment, Le Monde reports.
Socialists desert Hamon
Hamon has his problems with Macron, too.
Former prime minister Manuel Valls and his allies were to meet on Tuesday to discuss their next move after several of the party's right-wing defected to the centre candidate.
Hamon accused them of "stabbing him in the back", implying that Valls, whom he beat to the nomination in a suprise win in the party primary, may soon join them.
With Mélenchon overtaking him in the polls following last week's TV debate, he has been forced to criticise his fellow left-winger, condemning his wish for the European Union to normalise relations with Russia.
But Hamon's political adviser, former education minister Vincent Peillon, on Sunday called for the pair to renew their dialogue - and rally around the Socialist candidate.
Le Pen wants less Europe
National Front candidate Le Pen, for her part, laid into the European Union at a rally on Sunday.
"Germany dominates, imposing its politics and its choices but doing so against the interests of France and other countries," Le Pen told her supporters. "My choice is different. I want more France!"
Hollande, who is on tour in south-east Asia this week, could not escape the campaign.
"I still have work to do to prevent populism, nationalism and extremism from prevailing, including in my own country," he told a conference in Singapore.