The sequel rarely lives up to the original. From New Coke to “The Hangover Part II,” the follow-up to a classic often disappoints.

Expect the Donald Trump vs. Megyn Kelly rematch to do the same when the Republican presidential front-runner and his least-favorite journalist meet again on a debate stage Thursday night in Detroit. Kelly is too composed to pick a fight, so Trump would have to be the instigator. And since his Super Tuesday victories began a pivot toward the general election, he seems to be trying this new thing where he plays nice(ish) with reporters in an effort to look more presidential.

It’s possible, of course, that the hot-tempered billionaire will lose his cool. Things got pretty heated at the last debate (hosted by ABC News), and there is so much history and intrigue here that another epic clash would seem almost inevitable. It was the Fox News star who, as co-moderator of the very first debate in the campaign, asked Trump if he possessed a presidential “temperament,” given his many crude and insulting remarks about women.

Trump bristled at the question but took things to another level the next day, when he said in an interview on CNN that Kelly had “blood coming out of her wherever” — as if her tough-but-fair question was not a serious inquiry but a byproduct of PMS.

In the ensuing months, Trump ripped Kelly mercilessly on Twitter. She mostly ignored the nasty barrage but did tell Vanity Fair in January that Trump had previously been a steady — and perhaps slightly creepy — admirer, calling to compliment her show and sending Kelly news clips about herself, which he signed.

Trump denied those claims and tried to pressure Fox News into removing Kelly as co-moderator of another debate in late January. Fox refused, and Trump boycotted the event. He also skipped a town hall event hosted by Kelly last week, in which all other GOP candidates participated.

But he plans to show up on Thursday, and I expect him to be on his best behavior. Lashing out at Kelly after the first debate was all about showing voters that he takes no guff — just like America will take no guff when he's president. Walking away from the second Fox debate was all about showing that he refuses to make bad deals — just like America will refuse to make bad deals when he's president.

Lately, however, Trump has been trying to show that he's a "unifier." That was the theme of his Super Tuesday press conference, and it's clearly aimed at broadening his appeal now that he's the overwhelming favorite to win the Republican nomination.

"I’m watching your people on CNN," he said in response to a question from a CNN reporter, "and I’m watching the Fox people, and I’m watching the MSNBC people, too, okay? See? I’m becoming diplomatic."

There's no better way for Trump to show how diplomatic he can be than by treating Kelly with civility on Thursday night. So he probably will. And if he does, perhaps there will be stories about how Trump is a reformed man -- a serious person who is, just maybe, actually capable of "becoming diplomatic."

Despite all appearances, Trump's feud with Kelly really isn't personal. It's about making a point. He'll treat her however he needs to treat her to convey what he wants to convey.