A survey by the Ipsos institute commissioned by French public television and the daily Le Monde predicted a majority of those who backed candidates eliminated in the first round would switch to the frontrunner in the run-off.
A separate poll by Ifop for Europe 1 radio and news weekly Paris Match predicted a similar margin, with Hollande winning by 54.5 percent to 45.5 for the incumbent right-winger.
The polls showed that the attitude of Marine Le Pen's supporters would be crucial. Le Pen was the surprise breakthrough of the first round, winning just short of 20 percent before being eliminated.
She has not yet said which way she will advise her voters to turn before the Hollande-Sarkozy run-off, but Ifop said that 48 percent of her backers would switch to Sarkozy and 31 percent to Hollande.
But a third poll by OpinionWay said that only 18 percent of Le Pen's supporters would back the Socialist, while 39 percent prefer the incumbent.
AFP
