“I think it is now quite plausible that Nicolas Sarkozy will win the first round,” said Bruno Cautrès, a public opinion specialist at the Center for Political Research at the Institut d’Études Politiques, or Sciences Po. “I think this is a portentous moment. In means that, if he can maintain this momentum, a second round might be a very close race.”

Even before Sunday’s speech, Mr. Sarkozy had begun to aggressively court supporters of the far-right candidate Marine Le Pen, who has been gaining support among the working class and rural and younger voters who have been hit hardest by the economic crisis and government belt-tightening. Last week, Mr. Sarkozy took aim at immigrants, describing a France with “too many foreigners” and vowing to halve the number of foreign residents if re-elected.

The latest poll put first-round support for Ms. Le Pen, who heads the National Front, at 16 percent, little changed from the most recent surveys. On Tuesday, her campaign said she had formally qualified for the ballot by gaining the necessary 500 signatures of local officials.

The shift to the right has grown sharp enough to draw rare criticism from Germany. Foreign Minister Guido Westerwelle told Reuters on Tuesday that it was a mistake to advocate tighter borders. “Retreating into national shells is the wrong path,” he said.

The French in general are tired of Mr. Sarkozy and anxious about the economy and unemployment, at its highest rate in 12 years. But neither are they passionate about Mr. Hollande, who has never served in government.