Mayor de Blasio was in an auto workers’ union hall in Waterloo, Iowa — campaigning for president — when the lights went out in a 60-block swath of Manhattan.

“Restorations are underway with ConEd aiming to have ALL customers restored by midnight,” he tweeted.

But while Hizzoner was tweeting about the outage from afar, and scrambling to find a plane back to the city, his often-nemesis, Gov. Cuomo, was rushing to the emergency command center on the Upper West Side, where he planned to hold a press conference.

“I’ve been governor of New York for eight years,” he crowed on CNN. “In that time I can count the number of times I left the state on my fingers.”

Meanwhile, wags on Twitter were anointing City Council Speaker Corey Johnson as the de facto mayor.

“Power outage in Manhattan. Mayor @BilldeBlasio/@NYCMayor hasn’t tweeted about it, with the exception of one retweet,” scoffed Yashar Ali of New York Magazine.

“The Speaker of the NY City Council @CoreyinNYC has been tweeting updates for the past 30 minutes.”

Tweeted Nicole Gelinas of Hell’s Kitchen, “Mayor Corey Johnson has done a bang-up job during the last five hours. We have no idea what that random guy in Iowa is doing but good luck to him.”

“@CoreyinNYC is the de facto mayor tonight,” agreed New York One’s Michael Scotto.

The mayor said through a spokesperson Saturday night that he was heading by car to Chicago, where he planned to take a Sunday morning flight back to NYC.

“We have to have a system that is designed to handle disruptions and rather than domino, we have a redundancy in the system so this doesn’t happen” again, Cuomo told reporters at the press conference.

“We just can’t have a power outage of this magnitude in this city. It is too dangerous. The potential for public safety risk and chaos is too high. We just can’t have a system that doesn’t. It’s that simple at the end of the day and that’s what we’re gonna work on.”

The governor said he has directed the state Department of Public Service to investigate the cause of the blackout in hopes of preventing another of its magnitude.