Like crusaders marching into battle with little more than religious fervor for ammunition, a gaggle of first time candidates is seeking to unseat Maryland's two-term Republican Sen. Charles McC. Mathias in Tuesday's primary.

There are five Republicans running against Mathias, but the confident incumbent is buying no radio or television time to combat their message that he is a big-spending, big-government liberal, a Democrat in Republican disguise. Mathias and his aides are keeping a wary eye, however, on two hard-charging conservatives.

"He's standing in the middle of the ring, feet flat, and doesn't see the punch coming," said one, V. Dallas Merrell, a self-described "active Mormon" and defender of the family. He is financed, in part, by spirtual fellow travelers from out of state.

"I had to go to people who didn't know enough about Maryland to know what a long shot I am," said Merrell, 44, a business consultant whose treasurer and campaign manager are also Mormons.

"My Mormon upbringing has given me strength, honesty, self-discipline," said Merrell, who was president of United Families of America, a conservative lobby, until his last-minute decision to run for the Senate. "These are the very qualities people are looking for in a U.S. senator."

John M. Brennan, 40, an Annapolis attorney who claims close to 4,000 campaign workers "everywhere," is the other contender Mathias aides are watching. Since entering the race last August, Brennan has logged 60,000 miles across the state and raised close to $70,000.

His backers include the American Security Council Political Action Committee and several conservative Christian groups opposed to abortion and the Equal Rights Amendment.

Although Brennan and Merrell cover much the same ideological ground, Brennan said, "As far as I'm concerned, I have only one opponent and that's Mathias."

"Let's face it," said Dr. Roscoe G. Bartlett, a Frederick County farmer-businessman-teacher in the race, "almost all the votes we who are opposing Mathias get will not be votes for us but against Mathias. I've been at three or four forums with him. He gets nothing but polite applause. People who lambaste his voting record get loud applause."

Bartlett is hoping to win voters with his opposition to gun control. "One of the first things Hitler did was to pick up [citizens'] guns and then 13 million people went to the gas chamber," he said.

Gun control, he noted, is "not a major problem, but one bases his campaign on issues that help you win." So far, however, the strategy has brought him "a lot of moral support" but "not a lot of financial support" from the organized gun lobby.

Amounts and sources of Bartlett's financial support are his secret until after election day. "We very carefully staged our campaign" to avoid having to report contributions before then, he said, because such information "prejudices the voter."

Both Jack Fortune Holden and Gerald G. Warren. The other two candidates in the race readily report their campaign contributions. None.

"I've taken a public stand against campaign contributions," said Holden, a retired Army major who lists his occupation as law enforcement administrator but who is described by his employer, the Prince George's police department, as a "police clerk."

"It's a waste of money," Holden said. "I don't want my face on the floor. You buy literature and it ends up in the trash."

Warren, a Crofton lawyer, said he plans to mount a "Mac Attack" Tuesday.

"I'm trying to relate it to people who eat that McDonald's stuff," he said. That attack will be launched, however, without endorsements and without much effort.

For some of the candidates, being on the ballot and responding to the minimal amount of attention from newspapers and civic groups who want to know their views is effort enough.

"Most of my campaign has been spent responding to questionnaires," Warren said.