President Emmanuel Macron of France is liberalism’s new poster boy. Hailed as the answer to Europe’s populist tide, he has brought a buzz back into French diplomacy by facing down President Trump and President Vladimir Putin of Russia. “The Macron method,” a leading European think tank gushed recently, is the new Third Way, threading the needle between technocracy and populism.

At home in France, it’s a very different story. A recent poll found that Mr. Macron’s popularity fell by 14 points in August, after a fall of 10 points in July. Only 40 percent of respondents said they were satisfied with the president’s performance.

To be fair, Mr. Macron never had much popular support to begin with. In the first round of the presidential election in April, when the vote was split among four main contenders, he won just under 24 percent. (By comparison, François Hollande received 28 percent of the vote in the first round in 2012. Nicolas Sarkozy won 31 percent in 2007.) Mr. Macron won the second round handily, but only because he was the lesser-evil candidate in the runoff — his competitor was Marine Le Pen, the leader of the far-right populist National Front party.

Electoral arithmetic explains only so much. Mr. Macron’s popularity suffers from something more fundamental: Macronism. His entire political project has been far too focused on his personality. Much of his appeal has come from his youth, his dynamism, his good looks and his oratorical skills. This hyper-personalized approach always carried the risk that once his charm wore off, there would be nothing left for his supporters to like, which is exactly what is happening.