If this is what the Secret Service has become, it’s a wonder that something worse than Butler, Pennsylvania, hasn’t already happened.

That event was terrible enough, with one rally-goer killed and Donald Trump coming within an inch of losing his life.

If Trump hadn’t turned his head at the right moment, Butler would have become one of the most notorious locations in American history and we’d be living in a different world.

At the time, the Secret Service’s failure seemed unfathomable, and none of the revelations since — set out in a report by the Senate Homeland Security Committee –make it any better. Barney Fife was better organized and more accountable.

The Secret Service is given responsibility for avoiding a calamity that would traumatize the nation and derange its politics for years, perhaps decades, to come. Its competence is a matter of the utmost national consequence. Yet, the agency was bumbling and slow-reacting, a disaster waiting to happen.

Surely, this sort of ineptitude wouldn’t be tolerated by Taylor Swift’s security detail.

The story of how it happened is muddled by finger-pointing and confusion over who was in charge.

Secret Service advance agents didn’t know who was responsible for final decisions, and didn’t know who determined the security perimeter for the event. State and local law enforcement were responsible for the AGR building because it was outside the perimeter. But advance agents didn’t share planning documents with them, and didn’t ask for the operational plans of state and local law enforcement. Someone from Butler emergency services warned during a walk-through that local law enforcement didn’t have the manpower to lock down the building.

Advance agents did suggest putting large trucks or other heavy equipment between the stage and buildings to block lines of sight, but nothing came of the idea.

The local officers and Secret Service agents operated on separate radio channels, and the only communications connection between the Secret Service and police communication centers was via cellphone. Some agents’ radios had technical problems or didn’t work, while the counter unmanned aerial system was inoperative.

Crooks fired his shots at 6:11 p.m. At 5:44 p.m., the Secret Service security room got word that local police had spotted a suspicious person with a rangefinder near the AGR building.

This should have been a five-alarm event, yet key Secret Service personnel weren’t told that local police had observed Crooks and lost track of him.

Three minutes before Crooks fired, a local law enforcement officer sent a radio alert that someone was on the AGR roof, with the Secret Service security room getting word a minute after that.

When a Secret Service counter sniper saw local police running with their guns drawn toward the AGR building, it didn’t occur to him to tell Trump’s detail to get him off the stage.

He said the police running meant only an “elevated” threat level.