Born the only child of a middle class family, Donna McCullum grew up in Marshall, Texas, where her parents instilled on her a strong sense of values---and a love of politics. Donna's parents taught her that the greatest thing about America was that each and every citizen got to cast their own vote and play a part at deciding their own future. That idea appealed to Donna, and it strongly influenced her life.

Donna attended the University of Texas, where she was friendly with classmate Bobby Ewing. Donna had to drop out her junior year because her parents were killed in a car crash, and Donna was unable to sustain the costs on her own. However, leaving school did not fan her political flame. She got involved with local politics, often raising awareness of certain issues.

It was at a political function that Donna met Sam Culver, the former governor of Texas. He was immediately smitten with Donna, and Donna was taken by his wisdom and kindness. They both found that they had a great love of politics, and a mutual respect for one another. Even though there was a thirty-year age difference between them, they turned this mutual interests towards dating. Eventually, they married.

However, it became apparent that their relationship was one of platonic love and respect. Donna loved Sam, but as a friend and a mentor. Not as a lover. She quickly solved that problem one night in 1979, when she met the man that would change her life forever.

Lonely one night in a bar, Donna met Ray Krebbs, and found herself immediately attracted to him. She was still married to Sam, but did not tell Ray, instead captivated by his good looks and courting techniques. Eventually, Ray did find out she was married to Sam, and was infuriated. Donna promised to leave him for Ray, and he told her that when she did, they could be together. Donna promised she would, but never did.

A few months later, Sam died. Donna then re-entered Ray's life. He wanted to know why she did not break up with Sam as she originally had said she would, all those months ago. Donna explained that Sam was dying of cancer, and she promised to stick by him through his last few months, but know that he was gone, she was devoted completely to Ray. Donna and Ray were blissful---for a while. Eventually, their differences became glaring. When Donna inherited $10 million dollars from Sam's estate, Ray felt that was the straw that broke the camel's back. He and Donna were two different kinds of people---she was rich, he was poor (this was prior to Ray finding out he was Jock's son). Sadly, he and Donna broke up again.

Donna remained active in the world of politics, and it was there that she met Cliff Barnes, who was working on her for Dave Culver's (Sam's son) state senate campaign. She thought that Cliff was a handsome man, respected his politics, and enjoyed being with him, so she began dating him. But he wasn't Ray. Dallas is a smaller town than most think, so Donna kept seeing Ray. Eventually, they declared their love for each other, Donna broke up with Cliff and she married Ray.

They were happy for a while, until Ray's father Jock died. This plunged Ray into a deep depression, where he was always drinking and going out to bars. He even began an affair with a young bar girl named Bonnie Robertson. Donna caught them in bed together, but decided to fight for her marriage rather than give up. With her support, she and Ray set himself on the right track.

Around that time, Donna began writing a book on Sam's life called Sam Culver: The Early Years. While doing research for the book, Donna uncovered some very disturbing evidence that Jock Ewing may have maliciously swindled a man out of his rightful ownership of an oil property. Not wanting to publish this without first consulting the family, Donna told Miss Ellie, who grew furious at such a notion that her then deceased husband could harm anyone that way. Miss Ellie's reaction was one that resulted from not accepting Jock's death, and eventually, she realized that perhaps Jock had done this deal for he, too, made mistakes.

It was soon after that Donna was appointed as a member of the Texas Energy Commission, a newly developed organization that existed as a regulatory watchdog for the oil industry. While there, Donna clashed with J.R., who had obtained a variance that allowed him to overpump oil---not by legal means. Donna tried to put a stop to this, and with Bobby's help, did so. Meanwhile, Ray's cousin Mickey Trotter had come to live with the Krebbs' in an effort to "straighten" the wild teen out. His time with the Krebbs' worked, and Mickey matured into a sensitive man, but not before being involved in a car accident that paralyzed him and eventually forced him into a coma, where doctors informed Ray and Donna he would stay forever, kept alive by life support. Ray did not want this life for his cousin, and loved Mickey too much for this, so he pulled the plug on Mickey's life support, and was sent to prison. Donna stood by Ray through the arrest, the trial, and his eventual suspended sentence.

Donna and Ray's marriage was blissful. They found themselves working together, to solve the mystery of what J.R. had to blackmail Washington official, and Donna's old friend, Edgar Randolph with. All the while, they grew closer. But things quickly took a turn for the worse.

After Bobby was shot by his vengeful ex sister in law Katherine, he asked Donna to take control of his percentage of Ewing Oil, while he recuperated. While predictably causing clashes with J.R., Donna found that she REALLY liked the oil business. So, she bought her own field, and named it Krebbs #1. It was a huge success. This did not make Ray thrilled. He had always felt threatened by Donna's achievements---they made him feel like he was a loser and hadn't accomplished much, a feeling that was not aided by his already low self-esteem, the high profile of his brothers or his many failed business attempts. Thus, Donna and Ray's marriage began to suffer a lot of strain. Things only got worse when Ray joined the fight to save Ewing Oil from a lawsuit that Cliff Barnes and Jamie Ewing enacted in order to gain 2/3 of the company. Donna was against Ray's involvement in that, for fear that he would get hurt (after all, J.R. was involved!). Ray resented Donna telling him what to do---he was beginning to resent her. They grew more apart. Soon, Donna learned that she was pregnant, but decided not to tell Ray---she didn't want that to be the reason that they got back together.

Eventually, the two grew further and further apart. Donna did tell Ray she was pregnant, but that only led to more fighting. Donna and Ray separated, and she moved to Southfork. When J.R. suggested that Donna head up the lobbying effort in Washington to protect the interests of the Teas Oil Community, Donna saw an opportunity to work and perhaps get her mind off the troubles with Ray. So, she agreed to the position and frequently traveled to Washington D.C. to lobby. She and Ray just grew further apart, while Ray grew closer to Jenna Wade. Donna had to admit that she was jealous. But she had a male admirer of her own. Senator Andrew Dowling kept courting Donna, trying to ask her on a date, and get her to go to dinner. Eventually, Donna gave in and agreed.

As Donna and Andrew grew closer, Donna and Ray's divorce came through. She was very upset, but a bright light soon entered her life---the birth of her daughter Margaret. At that time, Donna and Andrew were very seriously dating, but Donna let Ray know that he could be a part of Margaret's life whenever he wanted. Soon after, Donna and Andrew married.

The following took place on Return to Southfork

They spent many happy years together, with Donna continuing her lobby effort and involvement in politics. However, Andrew was eventually diagnosed with Huntington's disease, and wasn't given long to live. Donna was crushed, but she continued with her work, as Andrew wanted her too. One project she lovingly oversaw was the dedication of a federal building in Dallas to her former father-in-law, Jock Ewing. Donna flew to Dallas for the ceremony. Ray was ecstatic to see her. The two discovered that their attraction was still there. He was having severe problems with Jenna at the time, which only plunged him closer to Donna. Despite both their married situations, they admitted that they loved each other.

However, fate took control, and both Andrew (from Huntington's) and Jenna (from suicide) soon passed away. After a period of mourning, Ray asked Donna to move in with him in Dallas. Donna, deciding to follow her heart and take a chance, agreed. She and daughter Margaret moved in with Ray and his son Lucas, and tried to make a life together. After settling in, it became apparent that Lucas resented Donna, feeling that she was trying to take the place of his mother Jenna.

It was soon after this that Donna and Ray got engaged and Donna decided to run for mayor. The campaign, combined with Lucas's recent problem child behavior, is starting to cause a rift in Ray and Donna, similar to the one that ended up in their divorce. So Donna is faced at a crossroads about what to do, for Donna has a love of politics, but she has a love for Ray as well. Donna does not want to lose Ray. Not again.