Addressing crowds massed at outdoor squares six miles apart, the conservative incumbent, and the Socialist challenger who could beat him, both claimed a turnout of 100,000 people.
Sarkozy brought forward his speech to just before Hollande’s in an apparent bid to dominate live TV coverage.
A rash of opinion polls suggests Sarkozy’s re-election hopes may be crumbling as a recent spurt in support appeared to be evaporating a week from the first-round vote on 22 April.
Latest surveys show Hollande regaining momentum for the first round and winning a 6 May run-off by between 9-14 percentage points.
“The future of our country is at stake,” Sarkozy told supporters gathered in the Place de la Concorde, the city’s biggest outdoor square and the place where King Louis XVI was guillotined during the bloody aftermath of the 1789 Revolution.
“One thing should count today. Where do we want to go from here?” he said, following warm-up speeches by political aides.
Addressing left-wing voters at a vast esplanade in front of the Chateau de Vincennes, a royal castle on the city’s eastern edge which a mob of workers tried to raze in 1791, Hollande said he could feel the country was on the brink of change for the better.
“I feel a great hope mounting from the depths of our country. A calm, firm, lucid hope of a change for the better,” he said in a speech broadcast after live coverage of Sarkozy.
“I am making an appeal to you today. You must come out and vote. Give me the force to win the election on 6 May,” he said.
Whereas Sarkozy stuck to recorded music and stayed behind crowd barriers, the blander but affable Hollande regaled his supporters, some of whom brought picnics, with live music from a Guadeloupean-style zouk band and mingled with the crowd.
The open-air contest came as Sarkozy is struggling to overcome a tide of resentment over the sickly economy and a widespread dislike of a presidential style some see as arrogant.
Open-air rallies are unusual for mainstream candidates in France, and the two rivals seemed to hope to mimic the buzz created by radical left-wing candidate Jean-Luc Melenchon, who has drawn huge crowds to his outdoor meetings.
While Hollande’s team seems visibly relaxed, Sarkozy’s aides are fretting that what started as a high-impact campaign has lost its vim. After pushing a hard-right stance on immigration and trade protection to attract far-right votes, Sarkozy is now insisting he stands for voters of all stripes.
“The Place de la Concorde has been touched by all of France’s history, it’s not about the left or the right,” Sarkozy’s campaign spokeswoman Nathalie Kosciusko-Morizet said.
“It’s a place where all French people can gather,” she said, speaking of the square, which is nonetheless known as the place where conservatives traditionally celebrate victories.
The near-simultaneous speeches are the closest the two rivals have come to a real-time contest, with no face-to-face televised debates planned until after the 22 April vote.
Hollande, whose aides have hit out at the conservatives for scheduling an outdoor rally to clash with theirs, indicated his choice of venue reflected his less combative campaign style.
“I am not asking for a head to be cut off, I am simply asking for another one to be chosen,” Hollande said this week.
The rallies were the climax of a week during which Sarkozy warned that a Hollande victory could spur a crisis of confidence among financial markets, prompting Hollande to accuse him of encouraging speculation to serve his political ends.