For many mothers and grandmothers, there’s nothing worse than having that good son, the smart one in the suit and tie, turn out not to have a lick of sense. Former Prince George’s county executive Jack B. Johnson was that kind of son.

The nattily dressed lawyer-turned-politician was adored by thousands of elderly constituents, mostly grandmothers who claimed him as their own. They doted on Johnson when he showed up to worship at their churches. And when he was invited to speak from the pulpit on, say, Mother’s Day, he made it sound as if he worshiped them all as well.

When Johnson would bring his own mother up from South Carolina and escort her, arm-in-arm, to special events, women in the audience would sigh in adoration. Now, with Johnson set to be sentenced Tuesday for taking bribes while in office, the grandmothers are sighing again, this time in exasperation.

“If his mother were still alive, she’d beat him with a broom,” Celestine Howell, 84, told me.

Howell was among some 1,700 elderly women who attended last week’s “Red and Gold Ball,” an annual luncheon in Greenbelt hosted by the county’s Aging Services Division. This was Johnson’s crowd, among his most loyal supporters. In his bid for reelection in 2006, the Red and Gold women’s brigade showed up at the polls in force and helped him beat former Maryland delegate Rushern L. Baker III by 5,000 votes.

Their reward? Seeing him hauled away from his home in handcuffs, dazed and ashen after being caught in a nickle-and-dime bribery scheme.

“I guess he just forgot to put his thinking cap on,” Olenzia Randolph, 83, said.

How could Johnson have been smart enough to go from being an okra-picking country boy to a big-time county executive, and then be dumb enough to risk it all for so little money that it could fit in his wife’s underwear? Questions like that keep a mother up all night wondering where she went wrong.

“The thing I don’t understand,” Dorothy Hawthorne, 75, said, “is he knew that he was being watched, and he still wouldn’t stop.”

Indeed, the FBI had been eyeing Johnson almost from the day he took office. And yet even as his closest associates were being called in for questioning and arrested, Johnson kept taking bribes.

“I was shocked,” Estella Thompson, 80, said.

For all of their collective mother wit and generational wisdom, the women simply couldn’t make sense of it. To them, Johnson’s downfall had been made more painful because his parents had worked so hard, and it seemed to have paid off.

Neither of Johnson’s parents had finished high school. His father was a farmer and dockworker, and his mother worked as a maid and cook. Johnson credits her with making education a priority in their home. And all of her 10 children — Johnson being the fifth — would go to college.

Johnson attended Benedict College in South Carolina, a small Baptist school founded for newly freed slaves. He helped pay his way by working as a custodian, assistant dorm director and counselor in a mental hospital. He studied business and accounting and made the dean’s list.

After a six-month tour of active duty in the Army Reserve, he came to Washington to study law at Howard. He went on to be elected Prince George’s state’s attorney. At the end of his second term as county executive, he got busted.

“It’s bad enough if your child drops out of high school and ends up hanging out on the corner,” Hawthorne said. “But it’s harder, I think, if he makes it past all of the hurdles and then, for no reason, starts cutting corners and blows everything.”

Part of what the grandmothers found so endearing about Johnson was that he unabashedly expressed love for his mother and, by doing so, honored them. Johnson believed in paying homage to his ancestors.

“Many of us are the descendants of those brought to this continent against their will,” Johnson said in 2002, at his first swearing in. “But we have risen beyond the shackles of slavery to a place of freedom, and with our vigor and our spirit, we join with all of our brothers and sisters to create Prince George’s County as a place of opportunity, freedom and fairness for all.”

Reminded of the occasion and Johnson’s soaring oratory, Hawthorne responded with what must be many a mother’s fear: “He might have known where he came from, but he didn’t know where he was going.”