Don’t think it was a mistake.
Trump is clever, he is betting he will get the nomination and when he gets the nomination the other candidates are stuck. . .why. . because the other candidates signed the same pledge and when Trump gets the nomination all those other candidates are required to throw their support to him because, after all, he will be the republican nominee.
Clever.
I thought about it some more and you’re right. He just partly covered his flank. We’ll never know for sure, but he probably cut a deal with the vipers in the rnc. Occam’s razor.
Jebito and the chamber of cronies are another challenge. But they were going to be anyway.