I’ve heard that, and if by it is meant “He could decide to stop running.”, then I agree with it.
If “he’ll make a gaffe” is what’s meant, then I think he has the money to turn around any problem with the way he says something.
If it’s true that Jeb has been calling Trump an asshole, then we know those same words from Trump would be plastered all over the media AND loudly proclaimed (again) as the gaffe that takes out Trump.
Why are they not the gaffe that takes out Bush?
If Trump takes himself out - it will be that his inner liberal sneaks out and is in contrasts to the true conservatives. I have my ideas on when/what issue that might happen.
But no moderator will take him out. Neither will Jeb. Or Perry.