Giles says his candidate can capitalize on all that chaos. Rivals may laugh, but Giles argues that if Carson can make a respectable showing in Iowa, then win in South Carolina — or at least come in second should a home-state senator, Lindsey Graham, run — and come in second behind Bush or Senator Marco Rubio in their home state of Florida, he could be positioned to make a real run. But that would depend on avoiding pitfalls like Carson’s ill-considered comments on homosexuality. Rather than capitalizing on the chaos, Carson may only contribute to it.

Ben Carson is, in many ways, the ideal Republican presidential candidate. With a not-too-selective reading of his life story, conservative voters can — and do — see in him an inspiring, up-from-nowhere African-American who shares their beliefs, a right-wing answer to Barack Obama. Before he was born, his parents moved to Detroit from rural Tennessee as part of the second great migration. His father, Robert Solomon Carson, worked at a Cadillac factory. His mother, Sonya — who herself had grown up as one of 24 children and left school at third grade — cleaned houses. When Carson was 8, Sonya discovered that Robert was keeping a second family. She moved, with her two sons, into a rundown group house. It was in a part of town that Carson described to me as crawling with “big rats and roaches and all kinds of horrible things.” Sonya worked several jobs at a time and made up the shortfall with food stamps. (Carson has called for paring back the social safety net but not doing away with it.)

Carson recounts this story in his best-selling 1990 memoir, “Gifted Hands,” which also became the basis for a 2009 movie on TNT, starring Cuba Gooding Jr. as Carson. Raised as a Seventh Day Adventist, Carson realized that he wanted to become a physician during a church sermon about a missionary doctor who, while serving overseas, was almost attacked by thieves but found safety by putting his faith in God. When Carson, then 8, told his mother his new dream, “She said, ‘Absolutely, you could do it, you could do anything,’ ” he told me. Forced by his mother to read two extra books a week, he made it to Yale, then to medical school at the University of Michigan, where he decided to specialize in neurosurgery. He was selected for residency at Johns Hopkins Children’s Center, where he was named director of pediatric neurosurgery at 33, becoming the youngest person, and the first black person, to hold the title. He drew national attention by conducting a succession of operations that had never been performed successfully, most famously planning and managing the first separation of conjoined twins connected through major blood vessels in the brain.

Carson, a two-time Jimmy Carter voter, traces his conservative political awakening to a patient he met during the Reagan years. During a routine obstetrics rotation, he found himself treating an unwed pregnant teenager who had run away from her well-to-do parents. When Carson asked her how she was getting by, she informed him she was on public assistance; this led him to ponder the fact that the government was paying for the result of what he did not view as a “wise decision.” The incident, he says, fed his growing sense that the welfare system too often saps motivation and rewards irresponsible behavior. (When we spoke, he suggested that the government should cut off assistance to would-be unwed mothers, but only after warning them that it would do so within a certain amount of time, say five years. “I bet you’d see a dramatic decrease in unwed motherhood.”)

Carson’s friends at Hopkins say they do not remember him being particularly outspoken about his conservatism. He devoted most of his public engagement to urging poor kids in bad neighborhoods to use “these fancy brains God gave us,” through weekly school visits, student hospital tours and, ultimately, a multimillion-dollar scholarship program. “His issues were always medical care for the poor, education for the poor, equal opportunity — helping the less fortunate and really inspiring them as an example,” a mentor who named him to the chief pediatrics-neurosurgery post at Hopkins, Dr. Donlin Long, told me.

Even when Carson got the chance, in 1997, to speak in front of President Bill Clinton, at the national prayer breakfast, he mostly discussed the lack of role models for black children who were not sports stars or rappers. (There was possibly an oblique reference to Clinton’s sex scandals, when he told the audience that, if they are always honest, they won’t have to worry later about “skeletons in the closet.”)

In 2011, Carson’s politics took a strident turn, mirroring that of many in his party during the Obama years. “America the Beautiful,” his sixth book, which he wrote with Candy Carson, his wife of 39 years, included a get-tough-on-illegal-immigration message and offered anti-establishment praise for the Tea Party. It suggested that blacks who voted for Obama only because he was black were themselves practicing a form of racism. (Earlier this year he admitted to Buzzfeed that portions of the book were lifted directly from several sources without proper attribution.) His prayer-breakfast performance in 2013, and the extremity of his remarks in the months afterward (Obamacare is the worst thing since slavery; the United States is “very much like Nazi Germany”; allowing same-sex marriage could lead to allowing bestiality), left some of his old friends bewildered. Students at Johns Hopkins University School of Medicine protested his planned convocation address there in 2013, and he eventually backed out. When I asked Carson about the view at Hopkins that he had changed, he said his themes are still the same: “hard work, self-reliance, helping other people.” If he had become more overtly political, he said, it was only because the Obama years had led him to believe that “we’re really moving in a direction that is very, very destructive.”