In a speech before the gilded statue in Paris of Joan of Arc, his heroine, Jean-Marie Le Pen urged French voters to back his daughter in Sunday's runoff.
"I will not forget anything and I will fight to the last second, not only against her project but against the idea she has of democracy and the nation", Macron declared.
Le Pen is also trying to win over those anxious about the anxious about the environment and paid a surprise visit Sunday to a factory whose waste is at the heart of a political debate on the Mediterranean coast.
The 56 year-old whose power base is in the suburban and semi-rural Essonne region south of Paris has always been sought by Le Pen as a potential ally.
French presidential candidate Marine Le Pen attacked rival Emmanuel Macron on Monday for his past as a banker and as someone who worked closely with unpopular head of state Francois Hollande during his five years in office.
Speaking in a Paris hall on Monday, Macron criticized Le Pen's "rude manners" and called her "the heir" to her father's politics.
But the same day 15 years ago - when the anti-Semitic, xenophobic Jean-Marie Le Pen shocked France and the world by getting past the first round to face off with Jacques Chirac - some 1.3 million people took to the streets against the FN candidate, including 400,000 in Paris.
Yet the gesture can not undo decades of anti-Semitism that still poisons her party.
Melenchon, for his part, offered the prospect of a second-round choice between two candidates who would tear up global trade treaties and whose presidencies could be fatal to a European Union already weakened by Britain's departure.
With less than a week to go, Le Pen, 48, and Macron, 39, are hammering home their arguments to voters as the two finalists in France's tumultuous 2017 election campaign. Macron once served as Hollande's economy minister.
At said press conference both leaders formalised a national pact whereby if Le Pen wins the May 7 elections, Dupont-Aignan will be appointed Le Pen's Prime Minister.
Le Pen's announcement came with the National Front again fighting a furore over a senior official's reported remarks about Nazi gas chambers. At a larger union rally nearby, some marchers carried signs reading "Let's block the National Front" - but no one was openly rallying for Macron. A party that was once considered a radical and insignificant group gained a majority of France's seats in the European Parliament in 2014 and now has the opportunity to hold the presidency. He strongly opposes Le Pen gaining power but has also refused to endorse Macron, seen as a pro-business figure who could reduce France's strong labor protections.
French presidential candidate Emmanuel Macron is taking selfies with elderly shoppers and shaking hands with asparagus and sausage vendors - and defending the European Union at a campaign stop with rural voters ahead of the May 7 runoff.
Cheers of "Marine President!" and anti-immigrant chants rose to the rafters.
Le Pen, who has courted the blue-collar vote, visited the Alteo aluminum plant Sunday in the town of Gardanne, but the event appeared to fall flat.