In a better America, Mitt Romney would be running for president on the strength of his major achievement as governor of Massachusetts: a health reform that was identical in all important respects to the health reform enacted by President Obama. By the way, the Massachusetts reform is working pretty well and has overwhelming popular support.

In reality, however, Mr. Romney is doing no such thing, bitterly denouncing the Supreme Court for upholding the constitutionality of his own health care plan. His case for becoming president relies, instead, on his claim that, having been a successful businessman, he knows how to create jobs.

This, in turn, means that however much the Romney campaign may wish otherwise, the nature of that business career is fair game. How did Mr. Romney make all that money? Was it in ways suggesting that what was good for Bain Capital, the private equity firm that made him rich, would also be good for America?

And the answer is no.

The truth is that even if Mr. Romney had been a classic captain of industry, a present-day Andrew Carnegie, his career wouldn’t have prepared him to manage the economy. A country is not a company (despite globalization, America still sells 86 percent of what it makes to itself), and the tools of macroeconomic policy — interest rates, tax rates, spending programs — have no counterparts on a corporate organization chart. Did I mention that Herbert Hoover actually was a great businessman in the classic mold?