Prince George's County Executive Winfield M. Kelly Jr. is fond of calling Gladys Spellman "Madame Tinkerbell." The nickname is derived from Spellman's seemingly magical ability to float into a room, spreading happiness and cheer among those present.

An exaggeratio perhaps. But Spellman, the two-term representative from Prince George's County - Maryland fifth Congressional district - appears to be as popular and certainly as well-known as any congressional candidate in the state.

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

Only one Democrat is trying to prevent Spellman from returning to the House for a third term - Davis J. Tomasin.

Tomasin is 25. He is energetic and has worked feverishly for a year on his campaign. He says he is closing on rapidly on Spellman and expects to catch her by the Sept. 12 primary.

"I knew when I first started this campaign a year ago that it would be an uphill struggle," Tomasin said. "And when you knock around for year talking to anyone who will listen, a lot of people are going to think you're crazy.

"I know everyone knows Mrs. Spellman and I know she is popular. But I think a lot of voters are going to be looking for change and I think they'll listen to what I have to say."

Spellman, 60, does not appear worried. She has appeared at meetings, forums and coffee klatches and spent much time in the county. Most Democratic observers see her as one of the few uncumbents in the area with little to worry about.

"Oh, I don't look at it that way," she said. "Anything can happen in an election, I really believe that. I'm just trying to get out and talk to the people and let them know what my record is."

Tomasin's says that Spellman's record is a shallow one and that her work for civil service reform and on behalf of federal workers "is only natural for someone representing a district like the Fifth which has so many government employes."

Tomasin graduated from the University of Maryland in 1974 and worked briefly for county executive Winfield M. Kelly Jr. He passes around a brochure full of proposals on subjects ranging from local crime to Fidel Castro's role in Africa.

"We need to elect more people who see the full fabric of things, who understand what our true needs are, who don't just supply short range answers," he said. "I was raised to believe in heroes. I think public service is the finest calling there is. That's why I'm in it."

The main focus of Tomasin's attack on Spellman has been her support of legislation, passed this year, designed to inject new income into the financially-troubled social security system. The legislation, Spellman concedes, will result in a tax increase.

"Mrs. Spellman claims that she had to vote for the legislation because it was an emergency, that there was a crisis," Tomasin said. "Well, if the Ways and Means committee had taken the time to make changes in the social security system, then there wouldn't have been a crisis and we wouldn't be faced with a raise in taxes."

Spellman, however, vigorously contends her vote on the Social Security issue was imperative.

"Too many things fail within the purview of the Ways and Means Committee right now and that should be changed even though it won't please the members of the committee," Spellman said with a laugh. "When I went to vote for the social security bill I could hear my opponent's voice saying 'she voted to raise the taxes.'

"But drastic action had to be taken. We didn't have time then to re-arrange the chairs on the Titanic. She was sinking too fast."

The Republican primary battle is between three men who have never held public office, although one of them has been trying to get elected to public office since 1970.

The veteran candidate is Frederick C. Taylor, a 62-year-old retired federal employe from District Heights. Taylor ran for the House of Delegates in 1970, ran for Congress in 1972 in Maryland's fourth district, and then ran in the Fifth district in 1974 and 1976.

Taylor is a conservative who says those who favor abortions should "put their money where their mouth is," and pay for all abortions. He is against President Carter's energy proposals and also against gun control.

One of his opponents, William A. Albaugh is a 55-year-old researcher and investor from Mount Rainier. He has no previous experience in public life.

Albaugh says he is running for four principal reasons: to protest the illegal removal of the District of Columbia from the state of Maryland; to protest the presient's and Congress' inability to understand the inflation and control it: to advocate socialized medicine and to advocate rapid development in the energy industry. Albaugh is in favor of abortion and gun control.

The third candidate, Saul J. Harris, 55, is from Landover Hills. He is a physicist who has held a variety of managerial posts both in government and private industry.

Although he has never run for public office, Harris has worked for the government at federal, state and local levels. He belives in abortion only for women under the age of 18 who are pregnant for the first time or in cases of incest or rape.

Spellman's high visibility, her reputation as one of the leaders of "Freshman Class" of a group of legislators electedin 1974 that reformed many of Congress's rules on seniority and committee appointments - and her reputation as the protector of the federal worker in a district full of federal employes would all seem to make her unbeatable both in the primary and general elections.

Nonetheless, Tomasin insists she can be beaten.

"Gladys loses votes when she campaigns," Tomasin said. "People are interested in issues now, not just personality. People want answers.

"I knew more than a year ago that this would be the right time to run. The governor's race throws things into flux and there's a growing animosity toward the organization and toward incumbents in general."

Tomasin speaks with great intensity leaning forward, drumming his fingers. He says he wants to win and means it.

Spellman is as relaxed as Tomasin is intense. The smile which helped earn her the "Tinkerbell," nickname never seems to leave her face. So some observers insist that behind the smile is a tough politican but is not going to get into a name-calling battle with Tomasin.

"I'm not running against him," she said, "I'm running for myself."

Spell won close races in 1974 and 1976 and Tomasin is optimistic about pulling off an upset this year.