Blas’ Biggest Mistake

Mayor de Blasio can’t decide just what his “biggest mistake of 2016” was. We’re happy to help. On the surface, it’s tough because he has so many choices — having the homeless-shelter population set record highs, letting that Rivington Street nursinghome flip sneak by, bungling oversight of the Administration for Children’s Services so badly that the state has demanded an independent monitor . . .

Not to mention debacles like the Lefty the deer fiasco, or his humiliating failure (again) to crush the humble horse-carriage trade.

Right now, the mayor likely most regrets his failure to heed Public Advocate Letitia James and crack down on ACS. As a father, he surely feels horrible about the deaths of little Zymere Perkins and Jaden Jordan.

As a politician, he’s got to be steaming at city Comptroller Scott Stringer’s new report outlining horrible ACS failures.

Including 38 deaths of vulnerable children who were on the agency’s radar, just in 12 weeks from July through September — 10 of whose homes had been the subject of at least four mistreatment complaints.

Stringer also faults ACS for gross mis- management — even after Team de Blasio bulked up the supervisory ranks — with bosses failing to properly review threequarters of high-priority cases.

In more than one-fifth of these most-urgent cases, ACS agents didn’t even meet with the at-risk child within 24 hours of an abuse allegation being filed, as required. Dozens of investigations got closed without ACS ever interviewing the little one.

As horrible as all that is, we’d advise the mayor to search deeper to identify his worst mistake — because the ACS horrors share a theme with most of his other chief disasters, such as the ever-growing homeless mess.

That theme is, at heart, a failure to manage — or even, really, to try.

De Blasio and his inner circle spend most of their time on politics and on his various ideas for remaking the city. Running things day-to-day is left to Deputy Mayor Anthony Shorris, plus burnouts like schools Chancellor Carmen Fariña and ex-ACS chief Gladys Carrion, as well as ideologues like homeless czar Steve Banks.

Time and again, the mayor leaves actual city government to run itself. Time and again, he’s shocked when it runs aground.

Will he ever learn from that mistake?