Regarding the special election Tuesday for the 5th District congressional seat that used to belong to Gladys Noon Spellman, Tom Mathers wants it clearly understood: If elected, he will not run again. If defeated, he will not run again.

"This is my first- and last-time run for anything," the 31-year-old Libertarian candidate declared. "I'm committed; this is it. I've given it a lot of thought."

"Don't put that down as a compaign pledge," implored Dean Ahmad, Mathers' campaign manager, chairman of the Maryland Libertarian Party and a self-employed astronomer. "I'm sure the Libertarians are going to want him to run again."

Mathers is indeed one of the stars in the tiny universe of Libertarians, a small constellation committed to the proposition that the government that governs best governs least.

But to date, Libertarians have captured only four elected posts -- two state legislative seats and a mayoralty in Alaska, and a town council position in South Carolina -- and there are only 60 registered party members in Prince George's County, which includes most of the 5th District. So, for the time being at least, the Libertarian message is mostly the medium.

"I can't believe it," said Mathers, fresh from a meeting with Washington Post editorial writers and an appearance on a radio talk show. "It's like if it's Tuesday, it must be Belgium's week."

Never mind that Democrat Steny Hoyer and Republican Audrey Scott studiously ignore the Berwyn Heights homeowner. On the radio Wednesday, Hoyer, for instance, pointedly referred to Scott as "my opponent."

"They don't want to draw attention to me," sniffed the snubbed, sideburned contender. "I never refer to them, either."

And never mind that Hoyer has raised $225,000 and Scott $102,000 to Mathers' modest $5,500, including his own $500 tax refund formerly earmarked to pay personal bills. When Hoyer and Scott clashed over the tone of their television ads, Mathers remarked, "I'm really lucky I can't afford TV advertising."

And while the Big Two brandish endorsements like mighty sabers -- labor heavies for Hoyer, big-name Republicans for Scott -- Mathers is glad to get the nod from a former president of the Gay Activist Alliance.

No matter. What's important is that, wherever Hoyer and Scott appear in a public forum, Mathers is likely to be there, too, quixotic to some, intriguing to others, but always a choice, not an echo.

Thomas P. Mathers, a child of the '60s, wore his hair "as long as they let it" at Washington's Archbishop Carroll High School. In 1968 and '69, however, he did his marching in Vietnam. His personal protest against the war was a vote for George McGovern in 1972.

A man in search of a party, he turned Libertarian in 1980, working for Ed Clark for president. When the Spellman seat was declared vacant and a special election called, Mathers suggested that the party jump in. Thirty members of the state Central Committee picked him. After a petition drive and a court battle, Mathers won a spot on the ballot.

As a Libertarian, Mathers opposes all laws against so-called "victimless crimes," such as prostitution and drug use. His opposition to govenment bail-outs for big business "goes without saying." On local issues, his position on the deficit-ridden Metro mass transit system is, "Sell it."

But Tom Mathers is also a realist who recognizes the short-term inevitability of big government. If elected, he promises to plunge into the bureaucracy, servicing the needs of his consitituents -- the meat and potatoes of congressional work.

To get to the Hill, he has taken his 12 days of annual leave and five days without pay from his job as a writer for the National Association of Security Dealers. "It's gonna be a long, hot summer for me if I don't win, because I don't have any vacation left," Mathers said.

But he hopes for the best and, as the campaign winds down, says, "I expect I'll be very gratified by the outcome." Come election night, Mathers said he plans to "wander over to my campaign headquarters, tap a keg and watch our victory tally roll up."