Maryland GOP Senate candidate Linda Chavez was ready to send her campaign brochures to the printer, but one problem remained: What should she use for a slogan? "Standing Up for Maryland, Standing Up for You" was her campaign manager's suggestion, but "it just didn't feel right" to Chavez.

After hours of discussion, her circle of advisers came up with the answer: "Made in the USA," which in Chavez's view not only evoked a sense of toughness and reliability but also bore a helpful resemblance to a popular Bruce Springsteen song.

The labored search for the right slogan and the right campaign theme has been repeated in recent weeks by all of Maryland's seven major Senate contenders as they prepare for the crucial summer months leading to the Sept. 9 primary.

On one level, the search for a theme reflects the candidates' efforts to gauge the sentiments of voters in 1986, as the Ronald Reagan era comes to a close and as the Democratic Party seeks a new course. It also shows the difficulty of carving out a niche in a field swelled by the retirement of 18-year GOP veteran Sen. Charles McC. Mathias, the turnover of the top state officeholders and the uncertain political fallout of the state's prolonged savings and loan crisis.

There are few obvious ideological differences between the four Democrats on one side, and the three Republicans on the other. As a result, each is groping for a way to separate himself or herself from the pack, whether through style, ideology, personality or message.

Baltimore Rep. Barbara A. Mikulski, the acknowledged Democratic front-runner, is a 49-year-old, 4-foot-11, quick-witted former social worker seeking to capitalize on her colorful personality, oratorical flair, and her record of advocacy. Gov. Harry R. Hughes, 59, the staid two-term governor and former minor league pitcher who was once the most popular politician in the state, is trying to promote himself as a moderate by highlighting his experience managing the state bureacracy. Rep. Michael D. Barnes, 42, an urbane Montgomery County attorney whose trademark is pin-striped suits and red ties, is hoping to use his reputation as a Reagan administration critic on Central America to portray himself as both a leader and a thinker. And Baltimore County Executive Donald Hutchinson, 40, a straight-talking former state senator who admires former Virginia governor Charles S. Robb and a generation of younger, pragmatic Democratic politicians, is trying to align himself with the new wing of the party.

On the Republican side is Chavez, 38, a photogenic Mexican American who hopes to use an extensive media campaign to try to repeat President Reagan's success in 1984 in wooing Maryland's ethnic and blue-collar Democrats. Chavez, a former Democrat and ex-White House aide, has grafted traditional GOP fiscal conservatism onto issues such as jobs and education that are usually associated with the Democratic Party. Richard Sullivan, 52, a tall, silver-haired, former Baltimore business executive, most closely fits the traditional Republican mold in a campaign that emphasizes his business savvy. Silver Spring lawyer George Haley, 60, brother of "Roots" author Alex Haley, has promised to broaden the Republican Party and to win over Democrats of all persuasions. In addition, several lesser known candidates have filed from both parties.

The array of strong and colorful candidates has attracted attention to the Maryland Senate race not only in the state but across the country, with political pundits seeing the race as a laboratory where both parties will test new ways of appealing to voters.

For the Democratic Party, Maryland offers the hope of recapturing defectors who gave the state to Reagan despite an almost 3-to-1 Democratic edge in registered voters. A victory in Maryland is seen as crucial to Democratic efforts to gain four seats needed to recapture the U.S. Senate.

For the GOP, Maryland is where the party hopes to prove that Reagan's victory among Democrats was not a fluke, and that conservative Republican candidates can attract traditionally Democratic voters even without the president on the ticket.

The advantage the GOP has is that Republicans are seen as good managers who are able to get things done, according to a recent voter study by Targeted Systems Inc. for the Democratic National Committee. But the public also believes that the GOP favors the wealthy and the interests of big business over those of average Americans, that the party taxes "unfairly" and has failed to handle the federal budget deficit.

On the other hand, the DNC study showed that voters believe the Democratic Party's "strengths revolve around values, human qualities and being 'for people.' " But voters believe that Democrats are fiscally irresponsible, disorganized, "wishy-washy" and unable to get things done.

In Maryland, there is another factor complicating the race. The yearlong savings and loans crisis has, according to a recent statewide poll, replaced jobs and other economic concerns as the issue most important to Maryland voters.

Of all the Senate candidates, Hughes has suffered most from the thrifts crisis and a resulting sense among voters that he has not been an effective chief executive. To counter the negative image, Hughes' advisers have pressed him to air television commercials later this month to assert that his handling of the crisis was an accomplishment, not a failure.

To distinguish himself from the two liberal members of Congress in the race, Hughes has begun to portray himself as the candidate most comfortable in the "moderate" wing of the party. In campaign appearances he has emphasized his managerial skills over his ideological leanings, and his campaign buttons so far have sported a lighthearted, and decidedly nonpartisan, "I'm wild about Harry!"

The moderate mold has not proven an easy fit for Hughes, who has espoused such liberal causes as civil rights, abortion rights and increased spending for public education throughout his 30-year career in public office. Asked about his ideology during a recent trip to western Maryland, where he invoked the themes of economic development and fiscal restraint, Hughes had a hard time specifying issues on which he is more moderate than his competitors.

"I think most people consider me a moderate as compared to Mike Barnes and Barbara Mikulski . . . although certainly not on civil rights," Hughes said. "What you're pointing up here is the problem I have with labels. Maybe in some few areas I am more moderate. It doesn't apply to civil rights. It doesn't apply to education. It doesn't apply to abortion."

Mikulski, too, is running a campaign that focuses on areas the DNC survey revealed as weak points for Democratic candidates. Her literature and speeches stress that she has "leadership, integrity and a framework for the future." She calls herself a "candidate who can get things done," and her advisers believe her punchy, direct style keeps her from being cast as "wishy-washy."

In addition, Mikulski's advisers believe that being an earthy, Polish Democrat will work to her advantage. "All the candidates are more or less the same on all the issues, so personality has got to dominate. It's the only way to make a distinction," said pollster Harrison Hickman, who is working for Mikulski and for Baltimore Mayor William Donald Schaefer in his bid for governor.

But tior citizens about fighting drugs and crime, and talking to a little girl about education.

But Hutchinson, who is trailing in the Democratic field, has not cornered that theme. Richard Sullivan, in a close fight with Chavez for the Republican nomination, is emphasizing that he is the only candidate with "real experience" in the business sector. Sullivan, the former top executive of Easco hand tool company, says that his past experience shows he has the qualities needed to balance the federal budget and bring jobs to the state.

In a state where roots are often important to voters, Sullivan also uses a slogan -- "A Marylander for the U.S. Senate" -- that stresses his 22 years in Maryland, compared with Chavez's two years in the state.

Of all the candidates, Chavez is using the riskiest strategy, trying to appeal to Democratic voters during a Republican primary campaign.

Chavez's "Made in the USA" theme is aimed at middle-class and conservative Democratic voters.

"Things made in the USA are tough and strong and reliable," said Chavez.

The similarity to Bruce Springsteen's song "Born in the USA" was a side benefit, she said. "I wanted something that caught you right away, and I thought, if people started thinking about Bruce Springsteen and then started thinking about Linda Chavez, I'll win the election."

Of all the themes, George Haley's may be the most direct. A former state legislator in Kansas and former government lawyer, Haley says he is most experienced at working with Congress and the federal bureaucracy. Lacking in the expensive consultants and pollsters who have come to the aid of the other candidates, Haley is running on the belief that as a lifelong Republican and the only black candidate in the race, he can both broaden the GOP and wage the most effective general election campaign.

Haley's slogan: "The Man Who Will Win!"