ROME — When Hillary Clinton warned in an interview this week that Europe’s centrist leadership needed to “get a handle” on migration, or risk further fanning the flames of populism, some wondered where she had been the last few years.

“We already did this,” said Italy’s former center-left interior minister, Marco Minniti, when asked about the comments. “She is talking about another era.”

Unauthorized migration to Europe has already fallen by around 90 percent since the height of the Continent’s refugee crisis in 2015, when more than a million asylum seekers, mainly from Syria, Iraq and Afghanistan, crossed into Greece and Italy. That precipitous drop is due in large part to Europe’s centrist leadership.

On Friday, facing some backlash for her remarks, Mrs. Clinton said in a series of tweets that it was precisely a centrist approach that she was advocating.