Dana Spellman O'Neill had something new to tell her ailing mother, Rep. Gladys Noon Spellman, during her regular bedside visit at Walter Reed Army Medical Center yesterday.

Every day since last Oct. 31, O'Neill, a 32-year-old interior decorator whose dark eyes and boundless energy are a reminder of her mother's once animated spirit, has sat at the bedside of the stricken congresswoman, describing the events of the day. Yesterday, according to O'Neill, she talked about her father's announcement that he will be a candidate in the special election to choose a new representative for Maryland's Fifth District.

"You would have been proud," O'Neill said she whispered to her mother. She also repeated what she said after the news conference in their Laurel home, that "Dad was nervous. I felt sorry for him. It's so different. Mom just blossoms when she is before the microphones."

O'Neill is certain that her mother "would be all for it," if she could but understand. But there is no indication that Mrs. Spellman, one of the most popular politicians to ever serve Prince George's County, has understood anything since she suffered massive heart arrest while campaigning in a shopping center last Halloween.

It is difficult for anyone who knows Gladys Spellman to picture her silent, unable to employ the quick wit that changed a thousand minds, and nearly that many votes, in a political career that began in PTA meetings, when O'Neill and her brothers, Stephen and Richard, were elementary school pupils in Cheverly.

Long after she advance to Congress, Mrs. Spellman's deepest interests, and political base, remained in local affairs. Even on Capitol Hill, she championed local causes, such as funding of the Metro rail system, and as chairwoman of a Post Office and Civil Service subcommittee, the problems of federal workers, many of whom live in her district.

To travel with Spellman around the district, which encompasses the northern half of Prince George's County and a tip of Takoma Park within Montgomery County, was to hear a non-stop history of the area.

"You couldn't drive by a park or a senior citizen's center without Gladys saying 'Remember that zoning battle,' or 'That [site] was one of our big victories,'" recalls Edna M. McClellan, her closest aide and friend.

McClellan, who sat on the blue carpeted stairs in the Spellman home as Reuben Spellman made his announcement yesterday, took a part-time job in 1965 at the courthouse in Upper Marlboro as a one-day-a-week, $1.75-an-hour typist for then-County Commissioner Spellman.

A penchant for meetings was a big factor in Spellman's success over the next 15 years. No crowd was too small, no cause too obscure. Her political advisers learned early in her career that "she is difficult to get out of a room. We had to give up door-to-door campaigning because she would spend an entire evening in one or two homes," McClellan said.

Spellman once got so carried away with shaking hands at a political testimonial that she fell off the edge of the stage. A moment later, she was up again, shaking hands and acting as though nothing had happened. One witness recalled, "It must have hurt like hell, but you would never have known it. That's Gladys for you. She never cracks."

Former Prince George's County executive Winfield M. Kelly Jr. is fond of calling his fellow Democrat "Madame Tinkerbell," a tribute to her seemingly magical ability to float into a room, bubbling with happiness and cheer.

"There is no one around I would like to run against less than Gladys," conceded one county politician. "There isn't anyone who doesn't know her."

She has her detractors, and before her illness, some were anxious to criticize her ability to always appear "on," simultaneously extending a smile, a handshake and a name, a trait she had perfected to the point that "it just makes you sick after a while," another critic said.

Her "mother hen" quality, though, is only a facade. While Spellman likes to point out that "I never raised my voice" during a debate in Congress, beneath that quiet, solicitous exterior lay a cunning, confident political pro. b

And Spellman has never been one to hide her accomplishments under a bushel. She talks with immodest detachment about many of the "good" things that occurred during her 12 years in county government. "It would have taken a lot more years to accomplish" zoning reform and other improvements if she had not been there, she has bragged.

Carlton R. Sickles, a former Maryland congressman and one of Mrs. Spellman's political mentors, acknowledged that some people think if Gladys -- and that's what she likes to be called -- as "pushy," but Sickles prefers to describe her as someone with "strength and drive."

The contrast between the robost, outgoing politician and the speechless, motionless patient at Walter Reed is difficult for the Spellman family to accept, even four months after the attack.

"It has been hell," O'Neill said yesterday before leaving her father's press conference for her daily vigil in the VIP ward of Walter Reed. O'Neill has talked to a lot of doctors since her mother was stricken and "I haven't met a smiling neurologist yet. Some say she could, some say she can't (recover). They give you a lot of averages, but I never thought of my mother as average."

During her visits she keeps her mother up-to-date on current developments, such as the latest antics of the four grandchildren, but she spends more time "reminding mom how unique she is. I keep pumping her about the past, keeping the stimulus going. We have a lot of memories."

But mostly O'Neill waits.

I'm waiting for her to look up and tell me to cut my hair, or to tell the boys to trim their beards," she said.

In the meantime, O'Neill said, forcing a laugh, "I've developed quite a monologue."