TAMPA, Fla. -- Josh Romney, one of the middle Romney boys and father of five, said Wednesday that he still calls his father "Dad" -- at least most of the time.

"I usually call him Dad, but sometimes Mitt slips out," he told NBC's Chuck Todd at the Atlantic/National Journal "Conversations with the Next Generation" event. "It's very weird," he chuckled.

Romney also revealed that he had no idea what his mom was going to talk about during her Tuesday night prime-time Republican National Convention speech.

He said he ducked questions from friends who wanted to know what his mom was going to say.

"I'd make stuff up," he said.

Romney said he was nervous for his mom, but thought she did an "amazing job."