PARIS — The embattled center-right candidate in France’s presidential race, François Fillon, called an extraordinary news conference on Monday to defend paying his wife hundreds of thousands of euros as his supposed parliamentary assistant, saying he had been the victim of a “media lynching.”

“All the facts are perfectly legal and transparent,” he said.

Before Monday, the air of scandal swirling around Mr. Fillon had led to speculation in the French news media that he would pull out of the race. Instead, he used the news conference at his Paris campaign headquarters to start a last-ditch effort to save his faltering candidacy.

Mr. Fillon lashed out at the news media, insisted that the work his wife had done for him was real, defended his own ethics and said he was staying in the race. “There has been a press campaign of unheard-of violence,” he told reporters.

Mr. Fillon’s troubles have grown with a string of revelations that he paid his wife and children nearly a million euros from public payrolls, prompting an investigation by France’s financial prosecutor.