My own prediction is that even if Ben Carson decides to run for president he will not, for all his manifold virtues, win the Republican nomination. This is not because Dr. Carson is unequal to the task, or lacks an army of admirers; it is because history and experience are ranged against him.

The appeal of the inspired amateur, the “nonpolitician” in politics, is strong in America, and over the years has propelled more than a few people into Congress ( Bruce Barton, Jim Ryun ), the Senate (S.I. Hayakawa, Al Franken ), and innumerable statehouses ( Jesse Ventura, Arnold Schwarzenegger ). Among Republicans, in particular, the allure of public-spirited businessmen—people who have built something from scratch, met a payroll, understand the economy and annual budgets—is especially strong. In the 2012 GOP presidential primaries, Herman Cain of Godfather’s Pizza fame was the beneficiary of this predilection; Steve Forbes ran in 1996 and 2000; Donald Trump has been toying with the idea for several cycles.

The problem is that impressive as certain individuals may be, the lack of political experience is a two-edged sword: They come to the hustings unpolluted by the partisan wars or tenure in Washington—but also as babes in the business of running for office. Lee Iacocca was a dynamic auto executive (Ford, Chrysler) with a well-developed sense of public relations, but practical politics was not his line. The only businessman-candidate to make much headway in modern times, H. Ross Perot in 1992, was a blunt-talking Texas billionaire with a high sense of self-regard and rough charm. But Mr. Perot turned out to have a dangerously thin skin, and his Reform Party quickly fell into comic disrepair.