[Heidi] Cruz, 43, grew up in San Luis Obispo, Calif., the daughter of a dentist and dental hygienist who are Seventh-day Adventists.

When she was 5, Heidi’s parents signed her up for piano lessons, and she insisted on practicing an hour and sometimes two each night. At age 8, when her parents first enrolled her in school, a family trip to Washington sparked an interest in politics. By fifth grade, Heidi announced she wanted to go to Harvard Business School.

“I don’t even know how she knew about Harvard Business School. It wasn’t in our world at all,” her mother, Suzanne Nelson, said in an interview. “A good word to describe her is ‘driven.’ I don’t really know what has made her so driven.”

[…]Cruz went to Claremont McKenna College and was active in the college Republicans and interested in appointive political office, said her mentor, Edward Haley. She also was intent on a career in business first. She moved to New York after graduation and worked on emerging markets at J.P. Morgan, an area in which she was interested after spending summers in Africa doing missionary work with her parents. She was put on the Latin America desk and taught herself to speak Spanish between 18-hour work days.

Cruz achieved her dream of attending Harvard Business School but turned down a job at Goldman Sachs to work on George W. Bush’s 2000 presidential campaign.

[…][S]he met Ted Cruz, who by his own admission turned off campaign colleagues with what he described as a “cocky” attitude. But not Heidi Nelson. She said he reminded her of “a 1950s movie star.” He grilled her on her hopes, aspirations and dreams during their first date. They were married the following year.

She was the star when the couple arrived in Washington, netting jobs at the Treasury Department and then the White House, working as a Latin America director on the National Security Council. Ted Cruz was floundering, and he moved back to Texas to become the state’s solicitor general with hopes of launching a political career. They lived apart for more than a year, until she gave up her job and moved to Texas.

After the move, she suffered through a period of depression.

“When I moved to Texas, it really was for Ted, and I wasn’t comfortable with that,” she told The Washington Post in September. She said she recovered with spiritual counseling. She started working at Goldman Sachs in Houston; she was promoted to managing director.

And she began to apply her talents to her husband’s political career.

[…]She now holds her own campaign events, talking up her husband’s values and laying out what the campaign sees as a grass-roots path to victory.

[…]She remains the campaign’s top fundraiser, now making many calls from the road instead of from the campaign’s airy Houston headquarters, where she installed a playroom with pillows decorated with raspberry prints for the girls. Cruz said she aims to make 30 calls a day but typically averages about 20 to 25; she is calling from the campaign and super PAC lists and trying to persuade donors to give the maximum allowed under federal election law.

“I don’t want to say it’s easy, and I don’t close every deal,” she said. “I think people want to be a part of something that addresses the main issue of the day, number one, which is Washington versus the people.”

[…]Ted Cruz told an audience in Winterset, Iowa, on Monday that the couple’s decision to run for president was difficult for his wife.

“Heidi spent a lot of years building a very, very successful career. And when we were deciding whether to run, particularly when you’re parents of young girls, that’s not an easy decision. And she was struggling with it,” he said.

Ted Cruz said his wife was driving, listening to a CD of Christian music sent by her sister-in-law. She was struck by a song about seeking the face of the Lord and pulled over on the freeway and started crying, he said. That moment, he said, “changed her heart,” and she decided that the race was about God, the country and the future.

Now, Heidi Cruz says her main job is to bolster her husband’s candidacy.

“There are women who use their husband’s candidacies for their own” purposes, she said recently while being driven to yet another airport. “I love my life. I love my career. This is not for me. This is for our country.”

In a glimpse into their marriage that Mr. Cruz called “illustrative,” he recalled saying to his wife in the weeks before his Senate primary, when he was still behind in the polls, “Sweetheart, I’d like us to liquidate our entire net worth, liquid net worth, and put it into the campaign.”

“What astonished me, then and now, was Heidi within 60 seconds said, ‘Absolutely,’ with no hesitation,” said Mr. Cruz, who invested about $1.2 million — “which is all we had saved,” he added — into his campaign.