A poll published last week showed that 41 percent of the voters who backed him in the April 23 first round did so out of tactical considerations rather than real conviction, believing he has the best chance of defeating 48-year-old Le Pen in Sunday's run-off.
But the boyish-looking ex-banker also attracts true followers, who see his youth, pragmatism and optimism as the best remedy for a country mired in economic decline and crippling self-doubt.
"A strong turnaround, that's what I'm hoping for from Macron," said Isabelle Babin, a 55-year-old executive who joined dozens of campaigners from the candidate's "En Marche" (On The Move) movement for a symbolic march on Saturday in the city of Lyon.
The former banker aiming to become France's youngest ever president may be "smooth, preppy and a little bit of a teacher's pet", she admits.
But for Babin, his private sector experience is a breath of fresh air in a jaded political system, whose two main parties crashed out of the election in the first round.
"They cannot understand society because they are outside of it," she said of his rivals.
'Only one choice'
Macron's meteoric rise from presidential advisor in 2012 to economy minister in Francois Hollande's Socialist government from 2014 to 2016 to presidential frontrunner has been attributed to a mix of talent, opportunism and sheer good luck.
His top spot in the first round triggered rejoicing among members of his year-old "En Marche" movement, which he has positioned as "neither of the left nor the right."
And yet while he still enjoys a double-digit lead over Le Pen in second-round polls, the gap is narrowing, forcing his troops to re-mobilise.
On Saturday, around 300 En Marche campaigners fanned out along the banks of the River Saone in Lyon to try to woo voters tempted to abstain in the run-off.
"There is only one choice, that of the republic and Emmanuel Macron," France's deputy sports minister Thierry Braillard said as he led the supporters.
In the first round, Macron polled 30.31 percent in the bourgeois southeastern city -- six points above his national average.
'Trust younger generation'
Campaigners there are confident of victory over the anti-immigration, anti-EU Le Pen, who has cast her rival as a puppet of the "oligarchy".
But they admit that their champion's mix of pro-business reforms and measures to boost take-home pay and integrate minorities has failed to garner much enthusiasm.
"He's too capitalist for people on the left and too tainted by Hollande's presidency for people on the right," said Emmanuelle Vignaud, a 43-year-old employee of a multi-national company.
Vignaud admitted that Macron had "messed up" the start of his second-round campaign, appearing "quite arrogant at a time when, given he is facing Le Pen, he needs to show gravitas."
"But he will be a very good president," she said, praising the intellect of the high-flying former philosophy student who attended France's top school for public servants.
Jean Visconte, a 64-year-old salesman, said he was seduced by Macron's youth.
"If we don't trust the younger generation, we're old fools who are beyond redemption!" he declared.
Others praised his attempt to transcend France's entrenched left-right divide, which has seen some accuse him of trying to be all things to all voters.
"Macron chose the only possible alternative in taking the best of both sides," said Alain Jacquard, a 75-year-old doctor, accusing the Socialists and right-wing Republicans whose candidates were eliminated in the first round of "spending their time demolishing what the other side did."
"Macron is a politician who believes in redistributing wealth on condition that we can generate the wealth," he said, summarising the candidate's programme.
That pragmatism has proven a hard sell among the 19.6 percent of voters who backed hard left radical Jean-Luc Melenchon in the first round, many of whom have announced plans to "go fishing" - French slang for abstentionism - on Sunday.
But on the centre-left, it has found fertile ground.
For Pierre, a 26-year-old civil servant and Socialist Party member who was among the campaigners in Lyon, Macron is the choice of the "realistic left".
"He can unite society," said the farmer's son.