"He doesn't lock himself in a room and memorize sound bites. That's not who he is," Eric Trump said in an interview with ABC News White House Correspondent Jonathan Karl and Political Director Rick Klein on the Powerhouse Politics podcast. "He speaks from the heart, he goes with his gut. He’s unconventional in that way, but that’s also what makes him endearing and compelling to some people."
While candidates traditionally hunker down and finish preparations the day before a debate, Trump will be flying across the country for a GOP event with House Speaker Paul Ryan on Saturday, ahead of Sunday's debate in St. Louis.
Trump's third-born child also blasted Sen. Tim Kaine's performance in the vice-presidential debate.
"There's no question that so many of those sound bites were written ahead of time, that they had been memorized and regurgitated," he said.
Asked if the GOP presidential nominee is doing anything different to prepare for his second head-to-head debate with Hillary Clinton after his shaky performance in the first debate, Eric Trump criticized the moderator -- NBC's Lester Holt -- for not asking Clinton about the 2011 Benghazi attack or the Clinton Foundation.
"He's having to fight the entire media as well," Eric Trump said of his father.
Eric Trump also defended his father's 3 a.m. tweets attacking former Miss Universe Alicia Machado, who Hillary Clinton mentioned in the first debate. The social media eruption dominated the news cycle for nearly a week, threatening Republican efforts to court female and Hispanic voters.
"At least he's up at 3 o'clock in the morning," the 33-year-old Trump said. "His energy level surpasses mine."
Trump also repeated his father's pledge to release his tax returns once the Internal Revenue Service completes its audit -- but did not say if he'll release returns from the previous calendar year.
Trump's campaign has not released any documentation from the IRS to prove he is under audit.