By conventional rules, Donald Trump should lose to Hillary Clinton in a landslide. But if God were enforcing conventional rules, Trump would be brooding atop his midtown Manhattan aerie, wondering how he came in last behind James Gilmore.

This has to terrify Clinton. She knows how to run against a normal Republican. Unfortunately for her, a normal Republican isn’t on the menu.

How would Trump win? The same way he won the primaries: by selling a more entertaining story.

About three years ago, the eponymous “Ace” from the legendary Ace of Spades HQ blog wrote a brilliant little essay on “The MacGuffinization of American politics.” “In a movie or book, ‘The MacGuffin’ is the thing the hero wants,” Ace writes. “Usually the villain wants it too, and their conflict over who will end up with The MacGuffin forms the basic spine of the story.”

The Maltese Falcon in “The Maltese Falcon,” the Ark in “Raiders of the Lost Ark,” the daughter in “Taken”: These are all classic MacGuffins.

Alfred Hitchcock apparently argued that it doesn’t really matter what the MacGuffin is, so long as the hero wants or needs it and it sounds important enough to justify the hero’s efforts. In “Mission Impossible 3,” we don’t even find out what the MacGuffin is, beyond being something very dangerous called “the Rabbit’s Foot.”

Ace’s insight was that the mainstream media covers President Obama as if he were the hero in a movie (with Republicans as the villains, of course).

Whatever Obama wants — ObamaCare, unconstitutional immigrant amnesty, the stimulus, a deal with Iran — isn’t important to a worshipful press corps. Whether policies are good or bad, lawful or unlawful, is kind of irrelevant. What matters is that the hero wants something.

“Watching MSNBC’s Chris Matthews interview Obama,” Ace wrote, “I was struck by just how uninterested in policy questions Matthews (and his panel) were, and how almost every question seemed to be, at heart, about Obama’s emotional response to difficulties — not about policy itself, but about Obama’s Hero’s Journey in navigating the plot of President Obama: The Movie.”

I think something similar has been at the root of Trump’s success. I can’t bring myself to call him a hero, but many people see him that way. Even his critics concede that he’s entertaining. I see him as being a bit like Rodney Dangerfield, constantly complaining he doesn’t get enough respect.

Regardless, Trump bulldozed his way through the primaries in part because the nomination was his MacGuffin and people wanted to see the movie play out.

Many voters, and nearly the entire press corps, got caught up in the story of Trump — much the same way the press became obsessed with the “mythic” story of Obama in 2008. People just wanted to see what happened next.

In the film “Wag the Dog,” a Hollywood producer and a political fixer conspire to get the president re-elected by concocting a fake international crisis in which an American soldier is taken hostage. They agree that the American POW has to be returned after the election. Why? Because as Robert De Niro’s character explains, that’s the final act of the story. The president needs to win the election for the audience to see the end of the story.

“Psychologically,” De Niro says, the voters “will understand that that’s the bargain. Make them pay for him . . . the price is their vote.”

This could be terrible for Clinton. She began her campaign thinking she could stage a remake of The Obama Story the way they’re remaking “Ghostbusters”: same plot, only this time with women. It doesn’t work that way.

Fair or not, the story of Hillary Clinton: First Woman President isn’t as exciting as Barack Obama: First Black President. And, more to the point, The Hillary Story is far less entertaining than The Trump Story.

Clinton is boring. She’s as fun as changing shelf paper on a Saturday afternoon. Meanwhile, who wouldn’t want to see a sequel to “Back to School” in which the Rodney Dangerfield character becomes president?

Everyone suspects they know what President Hillary Clinton: The Movie would look like. Trump: The Movie? That could be a wild ride.

Clinton’s best bet is to tell voters it would be a horror movie so terrifying, no one will want to see it. I’m not buying tickets to either show come the fall. But I’ll be following the promotions closely.