You'll need to pick your way through some inaccuracies that go to show how detached Trump was from the Georgia contest. Trump never mentions Kemp by name. From the Caller interview, emphasis ours:
The Republican governor of Georgia, he was down 10, and I endorsed him, and I think he won 70-30. He won by 40 points. I did that endorsement at the request and I liked him a lot. First of all, I have to really respect the candidate, I have to like the candidate, otherwise I'm just not going to get involved. But he's currently running as you know, he won the race against the man that was favored. But I did that for Sonny Perdue. But when I did it he was down about 10 points. And he ended up winning by 70-30. He won by 40 points, so that means he picked up 50.
Kemp, who is currently only the GOP nominee for governor, had indeed started the primary runoff behind in the polls, but as the July 24 election neared, he had in fact pulled even – or even slightly ahead – of Cagle.