Emmanuel Macron beseeched France to avoid voting for "Thatcher or Trotsky" or on Monday as the presidential campaign entered its final week ahead of a first round that is shaping up as a four-way cliff hanger.
The independent centrist pledged to "give France its optimism back" at his biggest rally yet before a crowd of 20,000 in Paris.
Shortly afterwards, the race's other frontrunner, Front National leader Marine Le Pen, held a rival meeting in the French capital - disrupted outside by anti-fascist militants and inside when a topless woman, thought to be a Femen activist, rushed onto the stage before being thrown out.
Polls in recent days have suggested that the race has narrowed considerably with Mr Macron and Ms Le Pen in the lead, but Communist-backed Jean-Luc Mélenchon and conservative François Fillon remain within striking distance.
Mr Macron mentioned none of his rivals by name, starting his speech with an ode to "France and its cathedrals" but insisting he was the only candidate he didn't have a fixation with the past.
The former economy minister who claims to be "neither Left nor Right" paid tribute to François Mitterrand, the late Socialist president, but also Jacques Chirac, the centre-Right Gaullist ex-president.
But it was clear who he was referring to when he said France should avoid voting between "Thatcher or Trotsky" - references to the Mr Fillon and Mr Mélenchon.
Mr Mélenchon, he said, would turn France into "Cuba without the sun or Venezuela without the petrol". The Leftist firebrand, who spent the afternoon on a barge going down a canal in Paris, is due to stage a rally in Dijon on Wednesday with his hologram appearing in six parallel rallies around the country.
Mr Macron later accused Mr Fillon of seeking power among other things to escape judicial "woes" - a reference to the fact he faces charges he use parliamentary funds to pay his British wife for a fake job but could be protected by presidential immunity if elected. He lacked the moral authority to rule, he claimed.
Mr Fillon, who denies wrongdoing, focused on shoring up the French Catholic vote over Easter and on Monday took his tough-on-security campaign to the southern French city of Nice, which was scarred by a deadly truck attack last year that killed 86 people. His speech was briefly marred by a heckler who shouted: "Give the money back."
"The campaign has been tough. My opponents from all sides have tried only one thing: to finish me off rather than debate," Mr Fillon told the crowd. "I surprised them once in the primary, we will surprise them a second time at the end of the week."
He hit back at claims corruption allegations disqualified him for the top job, saying that "thirty six years in the service of my country gives me more moral authority than the three years spent at Rothschild bank" by Mr Macron.
At her rally, Ms Le Pen re-formulated her oft-cited claim that the presidential election pits "patriots against globalisers", saying: What's at stake in this campaign is civilisation is either a French vision, or a post-national vision."
Promising an "immediate moratorium on legal immigration", she said: "Mass immigration is not an opportunity for France, it's a tragedy for France."
A daily Opinionway poll on Monday put Mr Macron and Ms Le Pen neck and neck in the first round of voting at 22 percent, with Mr Fillon at their heals on 21 percent followed by Mr Mélenchon on 18 percent.
Mr Macron was seen beating the far-Right leader in the May 7 runoff by 64 per cent to 36.
But a separate Elabe survey for L'Express magazine suggested Mr Macron had consolidate his lead on 24 per cent - up half a percentage point in a week - with Ms Le Pen also slightly up on 23 percent.
Mr Fillon's share of the first-round vote was forecast to slip to 19.5 percent, with Mr Mélenchon on 18 per cent.
Speaking after the Macron event, Michel Hascoet, 59, a businessman from Joinville-Le-Pont, predicted the race would go down to the wire. "I dare to hope that people will take into account the importance of France remaining in Europe, as the only candidate who is truly European is Macron.
"But many people will only make up their minds in the polling booth," he said.