Paris (CNN) -- The two contenders for the French presidency entered the final day of campaigning Friday, with opinion polls giving challenger Francois Hollande the edge over President Nicolas Sarkozy.
Sarkozy is holding a rally at lunchtime in the western Vendee area at lunchtime, while Hollande will address supporters later Friday in Moselle, to the east of France.
Campaigning ends at midnight Friday ahead of Sunday's runoff vote for the presidency.
It has been dominated by concerns over the economy, as France struggles to overcome low growth and 10% unemployment, and immigration issues.
A final opinion poll conducted by CSA for CNN affiliate BFM-TV and other outlets ahead of the second-round vote gives Hollande a 6-point lead over his rival, with 53% support to 47% for Sarkozy.
Hollande, speaking to French radio station RTL early Friday, suggested Sarkozy had miscalculated his Socialist rival's strength in the run-up to the vote.
"I have never underestimated Nicolas Sarkozy," he said. "I challenged his policies, his choices, his behavior, his ways, even during these last hours. But I know his energy, his strength of conviction and his talent as a debater.
"But, where he made a mistake was that he underestimated me. And in politics, he who underestimates (his opponent) overestimates himself and thus makes an error in judgment."
The two traded insults Wednesday night in the only televised head-to-head debate of the campaign.
Sarkozy labeled Hollande a liar and a "little slanderer," while Hollande accused the president of shirking his responsibilities, cronyism and favoring the privileged over France's poor.
Both Sarkozy, of the center-right UMP party, and Hollande have been working hard to reach out to France's undecided voters in the two weeks since the first-round vote on April 22 left them the only two still in the race.
Centrist Francois Bayrou, who took 9% of the first round vote, delivered a boost to Hollande's campaign Thursday when he said he would vote for the Socialist, and urged his supporters to vote according to their conscience.
Bayrou accused Sarkozy of lurching to the extreme right in the past two weeks of campaigning, as he attempts to appeal to the 6.5 million first-round supporters of the far-right National Front party, BFM-TV reported.
Those far-right views do not fit with the values of his MoDem (Democratic Movement) party, Bayrou told reporters in Paris Thursday.
Speaking on French radio Europe 1 Friday, Sarkozy questioned the logic of Bayrou's decision to back Hollande.
"He said that after much thought, he was voting Francois Hollande, and he added that this will lead to bankruptcy in February. Is that logical? It's hard to find coherence," he said.
"What's important is that almost all elected officials who support Bayrou joined me and I thank them for that. The others are free to express their own choice with their vote."
Marine Le Pen, who as leader of the National Front attracted nearly a fifth of the first-round votes, has not endorsed either candidate.
Saying she would leave her own voting slip blank on Sunday, Le Pen told supporters to vote "with your soul and your conscience."
In the April 22 ballot, Hollande received 28.6% of the vote, slightly ahead of Sarkozy's 27.2%. Le Pen, who has called for sharply curbing immigration, received 18% of the vote.
If elected, Hollande would be France's first left-wing president since Francois Mitterrand left office in 1995. Sarkozy has been president since 2007.
CNN's Saskya Vandoorne, Rachel Ramsay, and Azanie M'packo contributed to this report.