We know at least three reasons Mitt Romney won’t back down from appearing on a stage tonight with birther buffoon Donald Trump: the $2 million Romney is expected to raise at the fundraiser Trump is throwing for him in Vegas; Romney’s cowardice in ever facing down the Republican right (as the Obama video above only begins to hint at); and the probably accurate wager that any independents turned off by rants about Obama’s birthplace will forget who Romney liked to pal around with by November.

And we know why Trump wants to be on stage with Romney: to flaunt his powers and (in his mind) to avenge the humiliation he suffered last year when President Obama not only presented his long-form birth certificate but, at the White House Correspondents Dinner, made people laugh at Trump right in his face.

But maybe Trump, in his meanspirited, spiteful way, is also trying to hurt Romney. Not hurt his election chances so much as to stick it to him personally—to say to Mitt, “I own you.”

Consider: on the very day that Romney and Trump are to stand side by side, Trump upped the birther ugliness—as he did in this CNBC interview this morning, with Wolf Blitzer on CNN later in the day, and in this tweet in response to the Obama campaign video:

@BarackObama is practically begging @MittRomney to disavow the place of birth movement, he is afraid of it and for good reason. He keeps using @SenJohnMcCain as an example, however, @SenJohnMcCain lost the election. Don’t let it happen again.

Trump “is publicly challenging Mitt Romney to stay by his side even as the mogul makes birtherism his number one cause,” as TPM puts it. (In fact, it’s easy to misread the tweet to mean that Trump was saying that Romney is afraid of the birther movement and for good reason.) Trump can smell Romney’s fear not only of the birthers but of getting on the bad side of Trump. The reality-show star knows that Romney won’t speak out against him—and that only makes him want to see the possible future president of the United States pay obeisance to his nonsense. What a power rush!

Really though, I think that Trump might want to hurt—or at least leave his odor on—anyone who would take the mantle that was so briefly his: Republican frontrunner in the polls.

Wanting beyond all reason to be the center of media attention is, after all, the essence of Trump’s real résumé, and getting that media to fawn over his brilliance at getting media attention has always helped plump his bottom line. Nobody wants a dim-witted developer; they want a sharpie who can make the big projects happen.

That’s why Trump will forever hate on George Will for calling him a “bloviating ignoramus” on ABC’s This Week on Sunday. “Donald Trump,” Will huffed, “is redundant evidence that if your net worth is high enough, your IQ can be very low, and you can still intrude into American politics.” If there’s one pathetic thing we know about Trump, it’s how much he needs to convince himself and the world that he’s “smart.” He said it again today on CNBC: “I’ve been known as being a very smart guy for a long time.”

Will Trump go so far as to say something birthery on stage today, with or without Romney by his side? Even if it’s in some twisted form like, say, “I know some people don’t think Mitt Romney should appear on a stage with me because of my deeply held beliefs about where the president was born. But I’m here to tell you that’s why Romney’s your man—he stands by his friends, so let’s stand by him”?

And will Romney smile and produce one of those “inert” and “mirthless” laughs?