Don’t worry. Your secret is safe with me. And thank you for your service to the people of Gotham. (Charles Dharapak/AP)

I know why Mitt Romney won’t release his tax returns.

It’s as easy and as American as apple pie.

Long have I said that this campaign was unduly negative. It’s almost reached the point of physical discomfort. A candidate can’t walk down a hallway without being tied to a misstatement, stabbed several times in the back and forced to eat words that have been taken brutally out of context. It is so unpleasant that most Americans wish it were over already, and they wished that back in December.

So negative is this campaign that I ignored the obvious answer to the problem of Mitt’s tax returns, even though it was staring me in the face and I put a coat reassuringly around its shoulders when it was a small child.

I had begun to think, like everyone else, that the only reason Romney would not release his returns was something sinister. With all the pressure to do so, why hold out? Surely there was no point, unless what they revealed was a horrible secret, like a deranged first wife he and Ann had locked up in the attic, the fact that he had paid the past ten years of taxes exclusively in blood diamonds, or several tax-return-wrapped bodies that Chris Christie had lugged over after a rough day at the beach and begged him to keep secret.

What we already know about Romney is not exactly unembarrassing. He paid a mere 13.9 percent on the tax return we did see. His family has a horse named Rafalca, which sounds like every character in the fantasy novel you write at age fourteen. And according to his son, his idea of a good time is to drive around your yard removing tree stumps. He has all the suavity of Clark Kent, all the ostentatious wealth and inherited paternal hang-ups of Tony Stark, all the bizarre silver-spoon hobbies of Bruce Wayne and all the ability to generate believable dialogue of the comics pages’ Peter Parker. He has, in a word, all the bad habits of the superhero’s alter ego, with none of his world-saving gadgets.

Why let us see this, and not the tax returns? What could he possibly have to hide?

And then it hit me.

Mitt Romney is a superhero.

All the facts support it.

● His first name is Willard. Who these days is named Willard or Clark?

● This chart of how much money you require to be Batman places the figure at $682,450,750 — but if you subtract the estimated $600,000,000 to restore Wayne Manor, you are left with a much more manageable figure of $82 million-ish, well within Mitt Romney’s estimated $200 million-ish means. And if you eliminate the MittWing from the equation, it starts to look downright likely.

● Look at him. Button-down shirt. Salt-and-pepper hair. Awkward, grandfatherly manner, as though he’d just arrived from another planet or time period.

● Look at Ann. Everyone always comments on her grace, poise and tact, whereas Mitt wanders around saying that the trees in Michigan are “the right height.” This is a classic feature of the superhero’s love interest — several notches, as Mitt readily admits, above what he had hoped to be able to attract as a non-powered civilian.

● He has practice with crime-solving alter egos. During his youth, he used to pose as a police officer and pull over speeding friends.

● During the two years he spent abroad on a mission trip, no one sighted any superheroes.

● Recently defeated a zoo-loving eccentric known only as Newt.

● Why else would he not release those returns?

Clearly, he’s doing this to protect us, not himself. It is only due to SuperMitt’s tireless efforts that we don’t have masked supervillains and deranged lizardmen constantly bouncing around our streets. His financial non-disclosure isn’t a personal liability — it’s for the good of everyone. The horse, the dog, the minor ten-thousand-dollar flubs, the awkward never-unguardedness, these are all part of a persona. But when no one is looking, Mitt is swooping around the city, rescuing children from burning buildings, stopping catastrophes and defeating monsters of every ilk.

So we must push back against Harry Reid and his unbridled allegations. Harry Reid is a man, as Dana Milbank points out, known for calling people “fat” and “liars.” He may claim to have it from a nebulous source that Mitt Romney hasn’t paid income taxes in 10 years and that’s why he won’t release his returns. But even Reid admits that he doesn’t know whether his claims are true or not. And as Jon Stewart says, “Here’s a rule of thumb: If you have to follow your claim with the words, ‘I don’t know if that’s true,’ then shut up.”

But wait, you say! Do I know, beyond a shadow of a doubt, that Mitt Romney is a superhero? Well, I don’t think the burden of proof should be on me. He’s the one who hasn’t released his returns.

But hey, I’m as sure as Harry Reid.