An intruder made his way across the White House lawn and through the building almost to the Obama living quarters before being stopped by a Secret Service officer who was off duty: This chilling news is more than just a kind of melodramatic movie scenario come true.

Next to the military, the Secret Service is probably the most highly regarded institution within the executive branch. Or it was.

Now we learn its agents can’t catch a guy running across the White House lawn; can’t stop the guy at the front door; can’t get to him before he gets to the stairs that lead to the rooms where the president’s daughters sleep.

Which raises a simple question: If not the Secret Service, who? Whom can we trust to do a decent job in DC?

This fiasco — and the news, long covered up, that the White House was hit by several bullets back in 2011 — isn’t just a problem for the Secret Service and its present management.

This seems to crystallize a more general feeling that stretches from Washington to the far reaches of the globe — the feeling that things are spinning wildly out of control and there’s no one even minimally competent enough at the highest reaches of American power to calm the gathering storm.

We’ve all gotten used to the idea that Washington isn’t working well because of partisan clashes that have brought relations between the White House and Congress to a standstill.

Congress deserves the scorn it receives from the public; its approval rating is somewhere around 15 percent.

But incompetence isn’t the cause of gridlock; rather, gridlock is the result of passionate and profound disagreements. Nor is gridlock caused by confusion; everybody knows perfectly well what is going on.

The same can’t be said of the administration, which is awash in incompetence and confusion, much of it deliberate. Consider:

In the past week, the question has arisen whether the president refused to acknowledge the rise of ISIS over the past year or whether the intelligence community underestimated the threat.

Either the president is right and the intelligence community has presided over its worst failure since the Iraq war, or he’s wrong (or lying) and simply closed his eyes to a situation he did not wish to see. No matter which is true, it’s a disaster.

Elsewhere in the Middle East, we’re attempting to fight the Syrian regime by arming some rebel groups even as we serve the regime’s interest by going after ISIS.

The Daily Beast’s Josh Rogin reported Tuesday that “an airstrike from the American-led coalition nearly hit a command-and-control facility affiliated with the Free Syrian Army, the moderate rebels the Obama administration says are America’s ‘boots on the ground.’ ”

“Boots on the ground” brings up another example of administration incompetence: its inability to provide a consistent message to those serving in the armed forces and the American people in general about what we’re doing.

The president said there will be no ground troops — and almost immediately, Gen. Martin Dempsey, who works for him, said ground troops were a possibility.

And lest we forget, the administration’s bizarre handling of the US border and immigration policy in general led directly to the ongoing crisis involving tens of thousands of Central American illegals (many of them children) trapped in a no-man’s-land of detention centers.

This was the ultimate unintended consequence of a supposedly compassionate piece of public policy, one that the Obama administration has no idea how to rectify.

Also in the past couple of weeks came news that the total pricetag for healthcare.gov — for just the website, mind you, the portal to help you shop — came to more than $2 billion.

There are more examples, but only so much space. With more than two years left to his presidency, agency by agency, policy by policy, President Obama and his administration are running off the rails.