PARIS - French President Nicolas Sarkozy's re-election hopes suffered a double setback four days from the first round of voting when a string of public defections compounded the impression that his tumble in opinion polls is pushing victory beyond reach.

Former town planning minister Fadela Amara joined a growing list of political figures to desert the conservative Sarkozy and announce they will vote for his arch-rival, Socialist frontrunner Francois Hollande.

That followed the most devastating opinion poll for weeks, which showed Hollande has opened a five-point lead over Sarkozy in the first ballot next Sunday, and the Socialist has a yawning 16-point advantage in voting intentions for the May 6 runoff.

After a week of steady poll gains for Hollande, the CSA survey released on Thursday night gave him 29 percent of the first round vote, up two points from the institute's previous survey, versus 24 percent for Sarkozy, down two points.

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