HERE is a story about the promise of America. A boy grows up in rural Illinois, the grandson of a farmer who lost everything in the Great Depression. He goes to his small-town high school and then attends his state university, where he walks onto the basketball team and graduates Phi Beta Kappa. He does a stint in the Marine Corps Reserves, gets his M.B.A. and then goes to work for one of the Midwest’s regional banks.

In a different era, he might have stayed there for the rest of his career. But he’s lucky enough to be coming up in the 1960s and ’70s, just as the WASP elite is fading and the big East Coast institutions are opening their doors to strivers from all over. So our Illinois farm boy climbs and keeps on climbing.

He moves to New Jersey and goes to work for Goldman Sachs. He rises to become the company’s C.E.O., and a millionaire many times over. He goes into politics, winning a term in the United States Senate and then getting elected governor of New Jersey. When Barack Obama wins the White House, he’s discussed as a candidate for Treasury secretary. And when he loses his re-election bid, he returns to Wall Street as the head of a financial services company.

By now you may have guessed that I’m talking about Jon Corzine. If so, you probably know that his inspiring story has an unhappy ending — for New Jersey, which faced an enormous budgetary mess when Corzine left office; for his latest Wall Street firm, MF Global, which filed for bankruptcy last week after somehow mislaying some $600 million in customer money; and for the former farm boy himself, who resigned on Friday in disgrace.