The rally by the Left Front, which represents a coalition of leftist parties including the Communists, comes as Mélenchon enjoys a surprise surge in the polls.
With little more than a month to go before the first-round of voting in the presidential election on 22 April, Mélenchon this week passed the symbolic 10 per cent mark gaining more than four points since the beginning of the year.
The latest Ifop poll, released on Sunday, showed him with 11 per cent support in the first- round.
Mélenchon, a 60-year-old former Socialist minister who split with the party in 2008, appears to have won voters over with his virulent attacks on the rich, France’s political elite and European austerity measures.
Socialist candidate François Hollande, who has been leading in the polls, seems to have taken note of the threat and has suggested to left-wing voters that a vote for Mélenchon could hand victory to the right.
“Every vote is useful,” said Hollande when asked about the Mélenchon surge this week. “I don’t want to question this or that choice by voters, but everyone must understand what is at stake.”
The Ifop poll also saw Sarkozy moving ahead of Hollande in first-round voting intentions, although Hollande is still expected to comfortably win the second-round on 6 May.