LEO DUROCHER, baseball's veteran cynic, was wrong: nice guys can and, on occasion, actually do finish first. The most recent occasion, to our totally unrestrained delight, occurred in the Superdome in New Orleans on Tuesday night.

There, Sugar Ray Leonard -- a categorically nice guy -- of Palmer Park and Prince George's County, Md., regained the welterweight boxing championship from the man he had lost it to only five months earlier, the fearsome Roberto Duran of Panama.

Gasoline was 30 cents a gallon, and Sugar Ray Leonard was 15 years old, the last time Roberto Duran lost a professional prize fight. It was 1972, and Richard Nixon was still in his first term in the White House. Ray Leonard was in the Palmer Park recreation center learning his trade under the careful watch of Dave Jacobs. The last time -- before last Tuesday night -- that Roberto Duran failed to win, Sugar Ray Leonard was still 150 amateur bouts and four full years from his gold medal at the Montreal Olympic Games.

For Sugar Ray Leonard, boxing has not yet been that rendezvous with pain and injury. He has regained the championship with his body and mind whole. In fact, for some, his still unmarked and handsome boyishness was by itself probably enough to make him an underdog against the imposing Panamian.

Controversy remains over the way the championship fight ended. Roberto Duran, alleging cramps, withdrew in the eighth round. However, there was no doubt that Sugar Ray led on the scorecards of all three officials. Roberto Duran's own trainer, the venerable Ray Arcel, candidly acknowledged the same after the fight. Mr. Arcel, who at 83 was in the corner for his 19th championship bout, said simply of Sugar Ray Leonard: "Give him credit; he was completely in control."

Now Sugar Ray Leonard of Palmer Park and Prince George's County is the unchallenged champion. He has vanquished the man with "hands of stone." We admire his skill and his courage and his determination. We cherish him for his decency and for himself. Well done, Champ. Congratulations to Sugar Ray Leonard and to Palmer Park and to Prince George's County.