Mr. Fillon, who had sold himself as the image of rectitude, promised after the scandal first broke that he would withdraw from the race if he were criminally charged. But he later reneged on that pledge, prompting many supporters in his party and his campaign staff to desert him.

Since the first revelations, polls have shown Mr. Fillon likely to be eliminated in a first round on April 23. That would leave two candidates outside the major parties, including Marine Le Pen of the far-right National Front, to battle it out in the decisive second round on May 7. That unprecedented development, coupled with Ms. Le Pen’s newfound status as a contender against a former economy minister, Emmanuel Macron, has deeply unsettled political life here.

Mr. Fillon’s problems were compounded over the weekend by revelations of his alleged extravagant sartorial tastes. Reports, not denied by him, have said nearly 48,500 euros, or about $51,500, has been paid to a tailor since 2012 for fine suits, although it was unclear who made the payments. The newspaper Le Journal du Dimanche, which first published the reports, added on Sunday that an anonymous benefactor paid in February for two suits worth about $13,800 for Mr. Fillon, prompting Parliament’s ethics ombudsman to open an inquiry.

The new charges were expected, but they were announced a day ahead of schedule after Le Canard Enchaîné leaked the development over Twitter. Mr. Fillon had been summoned by investigative judges for Wednesday, but his lawyer said Tuesday that he had asked that Mr. Fillon meet with them a day earlier to avoid a large news media stakeout.

Mr. Fillon read a statement to the judges that was obtained by the newspaper Le Figaro. In it, the newspaper said, Mr. Fillon denied any wrongdoing, as he has done consistently before.