Ann Romney's horse qualified for the Olympics in the sport of dressage, which is also known as ballet for horses.
"She's the athlete," Romney said of his wife, Ann. "But in this case, it's not her personally, but she along with two other people purchased a horse, and have trained it up and it's done so well that the trainer and that horse are going on to represent the United States in the Olympics, in London."
Romney said he won't attend the Olympics to watch the horse, Rafalca, because he has "a campaign to attend to," but that "she's quite thrilled and I'm sure she'll be watching."
Romney said dressage has guided Ann through her bouts with Multiple Sclerosis.
"She's convinced [dressage helped] her regenerate her strength and renew that vigor, and so she cares very deeply about this sport and about horses.... I joke that I'm going to send her to Betty Ford for addiction to horses," Romney said.
Romney said Ann did not tell her about an MS flareup around Super Tuesday.
"She didn't mention it. She knew that if I'd heard a thing about it I would have shut her down and said you've got to go home, you've got to take some rest and see the people who give you care and get you tuned up again. But she knew it was important for her to keep working so she kept it from me and kept on working," Romney said.
Romney added: "She has been almost symptom-free ever since 2002, so almost ten years. And she has a great doctor and others who help her stay strong."
Romney also spoke about his father George Romney, the former governor of Michigan who launched a failed bid for the presidency in 1968.
"Every time I think of my dad, it tugs at my heartstrings. I mean, my dad was such an extraordinary person: born poor, raised poor, never graduated from college, never worried about the past, always looked forward, had such confidence in America that he went on to achieve great things in business and in government," Romney said.
"I look at my dad as one of a kind. Spoke the truth; he suffered for it politically time to time, but didn't care about the politics of truth. He said what he believed and moved on," Romney said.
George Romney's presidential bid never recovered after saying Americans had been "brainwashed" about the Vietnam War.
Romney said during debates, he wrote "Dad" on the top of each of his pages of his notes.
"Each time, I wrote 'Dad' at the top of my page, reminding myself of the sacrifice that he made in his life for his family, for us, and of his passion for America. So yeah, 'Dad' was just three letters at the top of the page," Romney said.