I’ve long suspected that if editors knew how little journalism occurs on the campaign trail, they would never pay our expenses.

Forget door-knocking. In reality, it’s more trainspotting. Reporters hang out at candidate appearances — and restaurants — talking primarily among themselves and comparing notes on which canned events they attended. (Did you see Santorum in Salem? No, I went to Romney in Hudson so I could catch Newt in Nashua.)

But this week something terrible happened. The Post’s op-ed editor, Autumn Brewington, joined me in New Hampshire — and discovered the reporters’ dirty little secret.

This year turned out to be a particularly wasteful one in the Granite State. Once Romney won in Iowa, the question was not whether he would win here but by how much. Yet the reporters descended anyway: Our hotel rooms were nonrefundable.

The good residents of New Hampshire, uninspired by the candidates, seemed less interested in attending candidate rallies than in years past. The result was that traveling mobs of journalists routinely outnumbered the “real people.”

As Jon Huntsman wound down his New Hampshire campaign with a stop Monday at Crosby Bakery in Nashua, he was trailed by about 150 journalists. Total number of New Hampshire voters: Perhaps a dozen. And some of them seemed more focused on taking pictures of “Meet the Press” moderator David Gregory than in seeing the candidate.

As I played sherpa for my editor, it was hard to conceal the fact that I was leading her on a journalistic road to nowhere. Among our first stops was the debate in Manchester, where one of the most embarrassing truths of campaign coverage was revealed: Reporters who attend debates aren’t even in the same room with the candidates. We take our seats in a gymnasium, plug in our laptops — and then watch on TV, like everybody else does at home.

While my editor watched on the screen in front of us, I attempted to look busy by sending out tweets: “Gingrich has now officially surpassed Churchill in jowls . . . Uh-oh. Sounds as if Perry is back on NyQuil.”

Next day, we headed to a Gingrich appearance that had great metaphorical promise: He reached out to Manchester’s Hispanic community by holding an event at Don Quijote’s Mexican and Caribbean restaurant. But it turned out to be more stagecraft for the media mob.

The campaign handed out “Newt Con Nosotros” buttons and had a local man with a Spanish accent introduce the candidate. A Gingrich daughter attempted what sounded like first-year Spanish on the crowd. But her proficiency didn’t matter, because two rooms in the restaurant, and a good part of a third, were crammed with journalists.

“All I see are white faces,” complained one news photographer. Instead of Hispanics, Gingrich found protesters outside (a few posed as a mariachi band and shouted, “Workers of the world unite”) and hostile questioners inside. “I’m not getting into a debate,” he told one of them. “You asked your question; you’re done.”

At a Rick Santorum event Monday, about 100 journalists and 20 TV cameras filled the chamber of commerce hall, where Santorum struggled with sound system feedback that sounded like a “Star Wars” lightsaber. “Is this bothering you? It’s bothering me?” he told the crowd, then turned off the microphone. “Can everybody hear me now?”

“Not for television!” one cameraman answered.

A moment later Santorum was back on the microphone.

After Mitt Romney spoke at a metal fabrication plant outside Nashua on Monday, the candidate took questions from reporters — who dwarfed the number of locals on hand. But even that was a made-for-TV special. Aides made sure that supporters waving Romney signs were the only people visible in the background. “We want the press out of here,” an aide said. They wanted the press out of a press conference?

Later, my editor and I retreated to Jackie’s Diner in Nashua, around the corner from the Huntsman event. Waitress Barbara Justason, 77, told us she had tired of the campaign events. “It’s all reporters and no real people,” she said.

The “real people” just weren’t into the campaign this year. “Usually I research everything and have big arguments at the counter. This time, I found myself not even wanting to read the articles in the paper,” she said. “Maybe I’ll close my eyes and it’ll be eenie, meenie, mynie, moe.”

That’s just what we were afraid to tell our editors: The New Hampshire primary just wasn’t much of a story.