The exact opposite is true - Trump has extended his lead nationally to 13 points, he leads by 18 in NH according to Monmouth and CBS News has him ahead by 15 in South Carolina. If he was going to 'fade,' it would have happened by now.
"Jeb Bush is part of a large group of people who are like the team at halftime who — like the Republican establishment, who feel like they’re down 50 points and they have decided they’re going to lose the game.
And that’s how the Republican establishment is right now. They don’t believe that Ted Cruz or Donald Trump can win. They think it could imperil their majorities in Congress, and yet they’re doing nothing about it.
...I thought Trump would fade. And I still sort of think he will fade. But it’s not looking…
Right now, Trump and Cruz are both looking pretty good. And I don’t think either is electable, and neither do a lot of Republicans. And so the question is, why do they just sit there and do nothing?"