Paris (CNN) -- Socialist candidate Francois Hollande declared victory Sunday in the first round of France's presidential election, setting up a showdown with incumbent Nicolas Sarkozy in May.

The proclamation, made to a crowd of supporters, is consistent with exit polls detailed on French television. Results from France's interior ministry show the same placement, albeit in a very tight contest.

With about 75% of votes counted late Sunday, Hollande had 27.9% support, followed by Sarkozy at 26.7%. Far-right candidate Marine Le Pen garnered 19.3% of this early vote, Jean-Luc Melenchon on the extreme left had 10.8% and centrist Francois Bayrou had 9.8%.

The gap had tightened appreciably from earlier results, when Hollande held a 6-percentage-point lead with just less than half the votes counted. Still, the order was consistent with exit polls that showed Hollande finishing with 28.4% of the vote, Sarkozy at 25.5% and Le Pen at 20%.

"I want to thank warmly the voters who, through their votes, have placed me in this position," Hollande told supporters in Paris on Sunday night. "This is an act of trust of confidence in my (positions) that I have presented to the French people."

The results set the stage for a May 6 runoff between Hollande and Sarkozy. Under French law, if no candidate wins an absolute majority, the two top candidates faceoff.

The results appeared to be historic, and a bad sign for Sarkozy. Several high-profile Hollande supporters told CNN that a French president running for re-election has never not placed first in the first round of the vote.

In his speech Sunday night in the capital, Sarkozy thanked citizens for voting during what he called "a time of crisis" -- saying "I know (their) worries, and I understand them."

He proposed three debates over the next two weeks, focused on the economy, social issues and foreign policy.

"The French people have the right to truth and clarity," said Sarkozy, who has been an outspoken leader on the global scene even as he has presided over a period of significant economic challenges since taking over in 2007. "Everyone will be able to make their choice with full knowledge."

Yet Aurelie Filippetti, an adviser to Hollande, said Sunday there would only be a single debate on May 2.

"There has always been one debate, and there's no need for (that) to change," she told CNN.

Sunday's turnout was 81%, with more than 12.5 million votes cast, according to the Interior Ministry. That marks a drop from 2007, when 84% of the nation's voters went to the polls, though key players from both Hollande and Sarkozy's camps described it as a "strong turnout" indicative of citizens' high interest in the race.

Especially with neither of them close to a majority, who assumes the presidency hinges on what support Sarkozy or Hollande can get from those who didn't back them Sunday. In his speech Sunday night, Melenchon urged his supporters to "fight against Sarkozy" -- noting that he's not "asking for anything in exchange" from Hollande for siding with him.

"I'm asking you not to drag your feet," Melenchon told his backers. "I just ask you to mobilize."

The 43-year-old Le Pen, though, did not specifically direct her own supporters to rally behind or against anyone in the runoff. In her own speech Sunday night, Le Pen described Sarkozy as "the outgoing president" and characterized her party as "the only opposition."

"We have never been as high as this," she said, pointing to her candidacy's vote tally. "This is only the beginning. Let us continue to fight."

Her National Front party -- founded and, until last year, led by her father -- has been known for anti-euro, protectionist policies, its stringent positions on curbing immigration and other more right-wing stances that would appear to jive more closely with the views of Sarkozy than Hollande. French Trade and Tourism Minister Frederic Lefebvre, a Sarkozy supporter, acknowledged to CNN on Sunday, "Now, we have to listen to the expectations of the far right."

Yet Ludovic Dedanne, a Le Pen adviser, accused Sarkozy of breaking promises during his five years in office and said people "do not trust" him. He recommended that his candidate's supporters "abstain" in the runoff.

Even as France has played key roles in international hot-spots in places like Libya and Syria, not to mention during the pan-European debt crisis, the domestic economy has been a prime focus of the election. France is struggling in the face of sluggish economic growth and a 10% unemployment rate.

A chief contrast in the two remaining contenders' economic approaches is that Hollande generally supports "more government action to stimulate the economy" whereas Sarkozy favors policies such as lowering some taxes and possibly repealing the mandated 35-hour work week, said Michael Leruth, who teaches a course about the election at the College of William & Mary in Virginia.

One year ago, Hollande wasn't even considered by many as the Socialist party's best hope. That distinction belonged to then-International Monetary Fund chief Dominique Strauss-Kahn, who polls suggested could challenge and possibly beat Sarkozy.

But Strauss-Kahn's political prospects floundered in the wake of a sexual assault charges -- later dropped -- after an incident at a New York hotel, as well as accusations he participated in a prostitution ring in France. That helped propel the 57-year-old Hollande, who has never formally held any national elective office, to become his party's presidential choice.

He is now aiming to become France's first left-wing leader since the late Francois Mitterrand left office in 1995.

Lefebvre described Hollande as "the choice of the past," with other Sarkozy backers playing up the fact that Mitterand didn't select him as one of his ministers during his 14 years as president.

Yet Filippetti said that Le Pen's strong showing suggested that Sarkozy couldn't get those more philosophically aligned with his views to support him, despite his "aggressive" efforts. That will leave the incumbent hard-pressed to unite all French, she said.

"The people ... don't trust Nicolas Sarkozy any more," Filippetti said.

CNN's Hala Gorani, Jim Bittermann, Saskya Vandoorne, Azanie M'Packo and Rachel Ramsay in Paris; Dan Rivers and Justine Redman in Toulouse, France; and Laura Smith-Spark contributed to this report.