Only three other people – Phelps, fellow American icon Mark Spitz and Kristen Otto, who won four golds for East Germany – have won four or more individual swimming medals at an Olympics.
That is the company with whom Marchand, seen as the successor to Phelps and coached by the US superstar’s former mentor Bob Bowman, now sits.
His races this week have been the most-sought tickets and the atmospheres the loudest, since an Antoine Dupont-inspired rugby sevens side won gold for the hosts at least.
The temporary swimming venue, built in an indoor arena that usually hosts the rugby union team Racing 92, was rocking once more with ear-splitting levels of support as Marchand came home in triumph.
His win was rarely in doubt. When he saluted the crowd after holding up four fingers he received a thumbs-up from Macron, who had just leapt from his seat in celebration.
“The guy is a machine,” said BBC commentator and former Olympian Andy Jameson.
Rebecca Adlington, 2008 double Olympic champion for Team GB, said: “After doing two in one night this probably felt at ease. It was fantastic.”