That search for ordinariness has been in conflict with her husband’s yearning for something bigger and the expectations long placed on both of them. Mrs. Bush has struggled to make peace with her husband’s world, but she is the furthest thing from a classic political spouse. If the 2016 election comes down to a choice between Mr. Bush and Hillary Rodham Clinton, she and Bill Clinton would present a startling contrast.

Mrs. Bush cherishes quiet lunches by herself, eating simple Spanish fare like jamón serrano at no-frills restaurants or painting in the studio of a friend, the artist Romero Britto, where her last work was of a little cat. When her husband was governor, she preferred spending hours touring women’s shelters and talking to abuse victims rather than highlighting her work against domestic violence to the news media. Her best friend is her sister, Lucila, who married a friend of Mr. Bush’s and lives just a few miles away.

“I have never heard Columba discuss the mechanics of politics,” said Ana Navarro, a Republican strategist and a friend of the Bushes. “I think that’s one of the things Jeb loves about her. He doesn’t come home to a spouse who’s been obsessing over political blogs all day.”