One private equity high roller says he knows a side of Donald Trump that's rarely seen on the campaign trail.

"I've known Donald Trump for almost 30 years. He's one of the kindest and most humble friends I've had," said Tom Barrack, the founder and executive chairman of private equity and real estate investment firm Colony Capital. "He's one of the smartest and most astute businessmen I've ever known."

"I actually think he can win," added Barrack. "America's ready to say 'Why don't we approach running America like you would running a business?' So, whether you like it or don't like it, what you're getting is unfiltered and raw from a guy who's writing his own checks. I think that's novel."