Latest opinion polls indicate Sarkozy could be struggling to keep his presidency.
Sarkozy's poor performance at the ballot box could spell trouble for German Chancellor Angela Merkel, his partner in the European Union's precarious balancing act between economic survival and looming sovereign defaults among the hard-pressed member countries.
Support for a second term for Sarkozy is waning, amid declining approval ratings for the president and gains made by Socialist rival Francois Hollande before Sunday's first round.
Ten candidates will face-off in Sunday's round of the presidential vote. If no candidate receives a majority, the top two candidates will compete in a run-off May 6.
MarketWatch reported since Sarkozy and Hollande remain within 7 or 8 percentage points of each other in preliminary voter polls, they will probably compete in a run-off.
Radio France Internationale said 29 percent of voters remain undecided or might not bother voting because of pessimism that neither candidate is capable of solving pressing economic problems, creating jobs, easing worries over immigration, French Islamic militancy or terrorism.
Hollande's pronouncements on French and European economic policies are starkly at odds with Sarkozy's austerity measures and EU's rescue programs for the euro and troubled member countries Greece, Italy, Portugal and now Spain.
If Hollande wins, that divergence is certain to bring him into direct conflict with Merkel and the European Central Bank, analysts said. The European compact agreed this year aims to punish countries that overspend and exceed their budgets.
Hollande wants to spend more to stimulate growth, a slogan that the French interpret as helping them back into jobs and other Europeans see it that way, too. French unemployment is running at 10 percent.
Opinion polls put far-right candidate Marine Le Pen third, with radical leftist Jean-Luc Melenchon close behind her, and centrist Francois Bayrou likely to come fifth.
Hollande also wants the European Central Bank to lend directly to troubled eurozone states rather than to banks, and keep interest rates low. This implies a major conflict within EU councils -- as the ECB cannot by law purchase government debt -- and also a dismantling of the EU compact, which expects member governments to balance their budgets or face fines.
French opinion also remains skeptical of Sakozy's claims that his partnership with Merkel has helped save the eurozone. More recently, opinion has also turned against the NATO-led operation in Libya that toppled Moammar Gadhafi but gave rise to a deeply divided, heavily armed and unstable country at Europe's doorstep.
Campaigning was to end at midnight Friday. French authorities have warned anyone leaking exit poll results before the close of voting at 8 p.m. CET Sunday they face a fine of up to $100,000.
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