He was the condemmed man, the death row inmate 13 hours from the electric chair who swore he wanted to die. She was the ex-girlfriend, a happily married Atlanta housewife, a beautiful memory from good times past. She heard about him on the radio and cried until he changed his mind.

Yesterday, on the day he was scheduled to die in Georgia's solid oak electric chair -- before the Surpreme Court affirmed a stay of execution Monday -- Jack Howard Potts 35, and Diane Nicholson, 33 announced their plans to marry. Someone in Nashville is bound to write their song; it's an all-American love story, pure Jonny Cash.

"I have left home and an filing for divorce," Mrs. Nicholson said yesterday as she announced her acceptance of Pott's proposal. He asked her to marry him last weekend in the visitors' room at the state prison near Jackson, Ga. Potts, a divorced father of four, was scheduled to die yesterday for the 1975 kidnap-murfer of Michale Priest of Roswell, Ga.

"I love him very much," said Mrs. Micholson, married for three years in Decatur, Ga., to a heating and air-conditioning contractor. "I'm going ahead and get my divorce as soon as possible."

Said Potts from his cell amidst 44 death-row inmates: "We were in love years ago and we are in love now. All Diane and I want is for people to leave us alone."

Nicholson's husband, Ed, 39, sat in their $72,000 brick split-level home, taking it hard. "I've been broken about every way a man can break," said the bearded contractor with a likeness to country singer Kris Kristofferson. He sank into the couch, chain-smoking Kools, a tattoo of a naked woman on one arm, a heart with "Diane" on the other. "It's like the country song, 'Diane if you're going to do me wrong, do me wrong with me.' I've watched my little piece of cake being slowly sliced away.

"It's been hell to sit here and watch her pick up the phone with Jackie and have her eyes light up like a teen-ager falling in love."

"This whole situtation has been very hard for me and my family," said Diane Nicholson, a tall, willowy blond who was to rendezvous with her husband at a nearby Dairy Queen last night to pick up her clothes and some money. "My family just can't accept my feelings for Jackie. They don't know what kind of person he is. I won't listen to people who says how bad he is. Things have just gotten to be too much. So I've left home."

She is staying temporarily at the home of Pott's defense attorney, Millard Farmer, the flamboyant, anti-death-penalty lawyer, whose Defense Team Inc. successfully fought for Pott's stay after Diane helped persude him, through a veil of tears, to sign the appeal papers June 4, the day before his first execution date.

But Potts changed his mind, two days later, telling a federal judg here he'd only signed the papers to make his family happy. Then he changed his mind again last week and his attorneys secured an emergency stay of excution from a federal appeals court in New Orleans.

Prison officials vow that the marriage will never take place. State rules allow for an inmate to marry only if his bride is pregnant with his child before he is locked away.

"I don't see why this case is any different from any other inmate in Georgia Department of Corrections. "And I'm sure it will be looked at that way."

Diane Nicholson said she wants to go through with the marriage even though she and her inmate sweetheart would be separated for the rest of their lives. Weekly visits across a wooden table, she said, would "be enough for me."

"They will be able to marry," bristled Farmer, a blue-jeaned aristocrat who itches for another constitutional fight over the prison regulation. "A prison can control certain things, but they can't control marriage. There is a lot of difference between an alleged rule of the warden and constitutional law."

Would he press for the wedding date with the same vigor he fought Potts' electrocution? "We're his lawyer," said Farmer, sitting in his cluttered Peachtree Street office beneath a poster that declared, "Capital punishment means them without the capital get the punishment." "We're his friends. We're in this fight for him."

The made-for-paperback love story has already been touted in the supermarket tabloids. "Killer's Long Lost Love Steps In From the Past to Save Him From the Electric Chair!" shouted a headline in the National Star.

Mrs. Nicholson said Potts and her first husband, presently an inmate in Gerogia's Reidsville State Prison and father of her teen-age son, were childhood friends. She interrupted that marriage to date Potts for several sweet months in 1967. They took off to Texas, Florida, drove all over the South has a fine time, she said. He treated her right. Potts was also married to another woman at the time.

He was an ex-con, the prodigal son of a suburban bricklaying contractor who never came back home, a juvenile roustabout who started out stealing cars, graduating to armed robbery and forging payroll checks.

"We were both married at the time, but we were in love," she said. They drifted apart. She moved in with Ed Nicholson for two years as he struggled with his buisness ans a messy divorce. They had met when Ed answered a service call and drove out to fix her air conditioner. They were married July 20, 1977.

"I hadn't seen Jackie in 12 years," she said. "We had our separate lives.

But he had been on my mind a lot and I had been wanting to get in touch and say 'I'm sorry.'"

She wrote him a letter. She told her husband, Ed, an ex-con who had made enough of a success with his heating and air-conditioning business to buy the family a camper, a speedboat, a fine house in the suburbs, tanks full of tropical fish, a black Peringese, two parkeets and a black Siamese cat. "Anything she wanted, I bought her," he said.

He didn't let her work. A traditional man with country-music values, he felt a woman's place was in the kitchen, "on a pedestal."

Ed encouraged her in her decision to contact Potts. He remembered how lonely it was behind bars, with no one to claim you.

She told Ed she wanted to testify before the Board of Pardons and Parole, to swear how well Jackie had treated her when they were together; maybe that testimony would help to persuade them to commute his sentence to life.

Potts wrote Diane back, asked her to visit him. He wrote that his sister had only visited him once in six years, that his brother, Billy, has only bothered to make it twice in four years. But he understood and forgave them.

It was in late May when Diane first visited her ex-boyfriend at the Jackson, Ga., prison -- a few weeks before his execution date of June 5 was stayed at the last minute by a federal judge in Atlanta. At that time, Potts had dropped his appeal, has converted to Catholicism and had sworn he was prepared to die rather than continue living in torment on death row.

Diane and her husband drove down to visit on June 1, and checked into the Vidalia Motor Lodge. Ed brought him a carton of Kools and chewing gum, and slipped him a note: "Don't slam the door as long as there's tomorrow, there's hope." But Potts was still hanging tough. The execution countdown was continuing.

Diane visited him for four days straight. The night before his date with the 3,000-volt electric chair -- the same whitewashed chair that had ended the lives of 415 inmates before it was shut down in 1964 -- the warden extened visiting hours and she stayed and cried and begged him not to die. His brother Billy urged him to live, too. He signed the appeal papers on Diane's lap.

It was perhaps the most bizarre twist in the latest case of death row brinksmanship, American style. Potts would have been the fourth inmate to die since Gary Gilmore stood before a 1977 Utah firing squad and said, "Let's do it."

Elated, Diane drove back home and told her husband, "Ed, I've got something to tell you. I think I'm falling in love with Jackie. I need your help."

Ed Nicholson said he had no idea. The night before Diane first visited Potts in prison, she left him a note: "If you don't want me to go, I won't. pI just want to try to help him.I don't love anyone but you. You must know that by now."

Then Ed found her diary with the scrawl, "Letter from "J." Even without asking, he knew "J" stood for Jackie Potts.

Still, she was reasurring him as recently as four days ago with yet another love letter, saying that the previous night they had spent together "was the best night of our marriage," Ed recalled, clutching her testimony as he sobbed on the couch. "She wrote, 'I love you very much. I know I can handle anything as long as I have your love. I will need you forever.'

"The next thing I knew, Diane was telling me. 'Four hours with Jackie Potts have been better than the whole five years with you.'

Replied Ed: "The worst moments with you have been wonderful."

Ed Nicholson, a philosophical man who was not too proud to beg, begged her not to leave him.He lobbied her parents, their friends. He stood by her side on Monday at the funeral of her mother, who died when her car hit a telephone pole over the weekend. He would do anything, he said even share her with Potts in a communal marriage, if that would keep them together.

"Yes, I'm willing to share he with him, if that's the only way I can keep her," he said yesterday. "Some might call me a weak son-of-a-bitch. Whether I am or not, I'm more of a man than most."

The phone rang in the living room. "She is divorcing me and marrying Jackie Potts, and I ain't s------ you," he told a friend.

He's willing to do anything to save the marriage. But he would rather lose Diane than have her by default, should Potts eventually die in the electric chair. "I love him and care for him." he said.

There is even an angry mother-in-law. Carolyn Potts, who has publicly urged on the execution so that her son might be put out of his misery, has had a series of confrontations with her daughter-in-law-to-be. "They're conning each other," she said of the wedding plans. "I'm just waiting to see which one cons the other most.

"Can you see someone on death row getting married? It's just a bunch of stupid stuff. They're making fools of each other."