Ted Cruz essentially gave a career-ending speech at the GOP convention on Wednesday night. It was a slap in the face to GOP nominee Donald Trump. This whole business about “vote your conscience” is a wonderful-sounding phrase. But we all know what he meant: Don’t vote for Donald Trump.

I was in the convention hall and the crowd’s reaction was unbelievable. It started out as a few hands waving in the air and some booing and then it just grew and grew throughout the entire convention hall. And then boom — as in absolute bedlam.

It happens that I’ve been to most of the GOP conventions since 1980, and I’ve never seen anything like it. These people stood on their feet and booed. These are Republicans. They don’t do this.

They don’t know how to stand up and boo. And yet, Mr. Cruz so divided them and worked them into such a frenzy that it happened. The Texan tried to pass it off as just the New York delegation acting up. But that is inaccurate. The whole hall was in an uproar.

Delegates couldn’t even hear the last two paragraphs of Mr. Cruz’s speech because the booing had reached such a crescendo. Mr. Cruz left an absolute disaster in his wake when he finished that speech. Everyone was dispirited, as anyone might expect.

And then came Mr. Trump running mate, Mike Pence.

What a terrific speech. He touched on all the major themes: The economy, shaking up Washington, and Trump being an outsider. He talked about how Mr. Trump understands that middle class wage earners have been hurt — they haven’t had a raise in 15 years. That’s something that Mr. Cruz, in all of his years of political experience, still doesn’t understand.

Really, in the space of about ten minutes, Mike Pence turned a demoralized, dispirited, depressed, negative convention into an upbeat, optimistic, united convention. He hit all the right notes and had a lot of optimism in his speech. The Cruz disaster, that had left the convention hall spinning just moments before, was suddenly swept away.

The entire hall started applauding Mr. Pence. Then they started cheering for Mr. Pence. And they got on their feet and cheered for Mr. Pence. Amazing.

Donald Trump couldn’t have made a better choice. Mike Pence single-handedly pulled that convention back together and united them with an optimistic message. He gave great support to Donald Trump and the ticket. He basically snatched victory from the jaws of defeat. He turned destruction into positive hope.

I’ve never seen anything like that.

Ted Cruz will never politically recover from this. His delegation from Texas wanted him to play ball with Mr. Trump, and he wouldn’t. He was freelancing in that speech. And that is why his political career is over. He’s finished.

But Donald Trump and Mike Pence are just beginning.

We have to wait and see what Mr. Trump does tonight in his speech. It could make or break his presidential campaign. I personally hope that he puts a lot of focus on optimistic, positive changes for America. I want to see a lot about growth in that speech. I want to hear him talk about lowering taxes and curbing regulations.

But here’s what I want to see most of all: a follow-through from what Mike Pence started. One of Mr. Pence’s messages on Wednesday night was that we, meaning the ticket, can turn this nation around. It’s an American malaise right now — from the economy, to civil unrest, violence and the threat of terrorism. And that is what Mr.. Trump must prove to the nation and the world, that he can turn it around. He’s got to convince them.

It’s kind of like Reagan redux. Ronald Reagan was able to do this. He proved that he could do the job. That’s what Mr. Trump needs to do. That’s huge. That’s more important than any policy detail. That’s the spirit that Mike Pence started on Wednesday night. Let’s hope Mr. Trump does the same.