CLEVELAND — We all know what Donald Trump has brought to this presidential campaign. Wednesday night, Mike Pence finally brought the stuff that was missing.

Calm, sober, exuding heartland decency, a guy who grew up in front of a cornfield brought a sleepy, surly crowd to its feet. Just an hour or so earlier, Trump’s delegates, led by a vocal Empire State faction, shouted down Treacherous Ted Cruz for failing to offer even a pro forma endorsement of the GOP nominee and finally booed him back to Texas.

No GOP convention anyone can remember has ever before had to stumble through its convention worried about nailing down the votes of its core demographic of Arnold Palmer-drinking, God-fearing, flag-saluting country-club Republicans.

Pence’s speech told these voters: I’m here. I’m proof that we’re still the same party. If you’re worried about who will provide adult supervision in the White House, look no further.

Both party conventions usually go off so smoothly that it’s easy to overlook the potential for disaster. Nobody wants the Message to be occluded by accusations of plagiarism, much less by the nightmare spectacle of the delegates practically coming after the second-place finisher and supposed unifier with pitchforks and torches.

Pence, starting out with his trademark line, “I’m a Christian, a conservative and a Republican, in that order,” segued beautifully into the kind of gentle, self-deprecating humor that always works well in politics — but especially well in a season of anger and hyperbole.

Of Trump, Pence said, “He’s a man known for a large personality, a colorful style and lots of charisma. So I guess he was looking for some balance on the ticket.”

Then Pence did the thing that no other speaker this week, except Donald Trump Jr., could quite manage: Without sounding like it was wishful thinking, he cogently fused his brand of old-fashioned conservatism with Trump’s bold new direction. He wrapped it all up so it was as pretty as a package from the little neighborhood jewelry store around the corner from Trump Tower, the one his younger daughter is named after.

Talking about an economy that has borrowed massively yet barely delivered a pulse, Pence said, “The national debt has nearly doubled in these eight years and [Hillary Clinton’s] answer is to keep borrowing and spending . . . they tell us this economy is the best that we can do. It’s nowhere near the best that we can do. It’s just the best that they can do.”

Serene and mature, Pence provided the superego to Trump’s id, yet identified their common ground: They’re both so indisputably American. “He’s the genuine article,” Pence said. “He’s a doer in a game usually reserved for talkers.

“And when Donald Trump does his talking, he doesn’t tiptoe around 1,000 new rules of political correctness. He’s his own man, distinctly American — and where else would an independent spirit like his find a following than in the land of the free and the home of the brave?”

Pence proved to be an adept attack dog, too. Gently, almost politely, he tore Clinton apart without the red-faced shoutiness other speakers showed, the kind commentators easily dismiss as nutty raving.

The crowd here at Quicken Loans Arena has, not entirely to its credit, taken to shouting “Lock her up!” whenever the Democratic Party nominee is mentioned. They did so again when Pence brought her up.

But instead of taking his cue from the crowd in the room, Pence made a subtly damning case to TV viewers: “Over in the other party, if the idea was to present the exact opposite of a political outsider, the exact opposite of an uncalculating truth teller, then on that score you’ve got to hand it to the Democratic establishment, they outdid themselves this time . . . At the very moment when America is crying out for something new and different . . . Democrats are about to anoint someone who represents everything this country is tired of.”

That isn’t Trumpian bluster. That’s succinct, direct, reasonable and devastating. Trump-Pence may be a match made in politics, but this could be the beginning of a beautiful friendship.