What's the one piece of advice former congressman and presidential candidate Ron Paul has for his son, Sen. Rand Paul (R-Ky.), ahead of a possible 2016 White House bid?

"I would say be very cautious; you could get elected," the elder Paul told NBC's Jay Leno on Thursday.

Ron Paul said he views his son as a tea party guy and that he was surprised by how much success he had as an underdog Senate candidate in 2010.

"I didn't think he would do that well," he admitted.

And what about his 2016?

"I've never talked to him about it," Paul said.