By Brooke Nevils

Rock Center

LLANGYNWD, Wales - About two hundred miles away from the Greenwich, England, arena where her purebred horse Rafalca competed in the London Olympics, Ann Romney stroked the nose of Magic, a Welsh pony.

"You're so pretty, Magic," said Mrs. Romney.

In the rugged coal country of southern Wales, you see a different side to Ann Romney: she is at one point teary-eyed, another laughing, but always a tough defender of her husband. She talked at length about her life with multiple sclerosis, her conversion to the Mormon faith and her decision to stay home to raise her five boys.

As Rock Center Correspondent Natalie Morales found in her exclusive interview with the wife of presumptive Republican presidential candidate Mitt Romney, scheduled to air Thursday at 10pm/9c on NBC's Rock Center, this coal miner's granddaughter is much more than an owner of an Olympic dressage horse.

Mrs. Romney is a first-generation American. Her father, Edward Davies, emigrated to the United States from this part of Wales in 1929, at age 15.

"It's very emotional for me to come back and to know what kind of life my grandfather lived, and my father," said Mrs. Romney, touring a coal mine much like the one in which her grandfather began working at age six.

The Davies family settled in Detroit, where a nearly 16-year-old Ann met 18-year-old Mitt at a party, and the high school sophomore's "heart went aflutter." Four years to the day after their first date, they were married.

"We are partners, true partners in every sense of the way," she told Morales. "I don't think he could do it without me. I don't believe he could. I couldn't obviously be here without him either."

Despite her steadfast support on the campaign trail, Mrs. Romney -- much like her sons -- was not so keen on her husband's role in public life after his failed bid for the Republican nomination in 2008.

"After the election was over and [John] McCain was the nominee, I made a decision that I would never do it again," she said. "You know who your husband is. You know-- I know what a good person he is. And oh - the negative - it's so hard as a wife to sit there and listen to that."

But when Morales asked why she changed her mind, Mrs. Romney said, "We have a reason why we're running and it's because I believe in my heart that Mitt is going to save America, that economically we are in such difficult times and that he is the person that’s going to pull us through this."

The criticism that plagued the Romneys during the 2008 campaign has continued, particularly in regards to their reported $250 million fortune and the issue of their tax returns.

When pressed by Morales, Mrs. Romney stood her ground. "We have been very transparent to what's legally required of us,” she said. “There's going to be no more tax releases given."

Mrs. Romney said if they release any more information, "it will only give them more ammunition."

In regards to their finances, she said "there's nothing we're hiding."

"It's been managed by a blind trust since before Mitt was governor, you know, 2002 forward,” she told Morales. “And so, you know, I'll be curious to see what's in there too."

Editor's Note: Natalie Morales' full interview with Ann Romney aired Thursday, August 16 on NBC's Rock Center with Brian Williams.