Glucksmann's rally aims to solidify his position in the upcoming election.
He faces pressure from the rising popularity of radical left candidate Mélenchon.
The decision on his candidacy is expected within three months.
French presidential election: Raphaël Glucksmann seeks to dispel doubts with high-stakes rally
The center-left MEP has given himself three months to decide whether to run for president, raising questions amid the momentum of rival Jean-Luc Mélenchon.