For Rep. Benjamin Cardin (D-Maryland), the major challenge in his first reelection campaign has been not so much how to get people to vote for him, but how to get them to vote period.

In a primary campaign in which he is opposed by only one Democrat, Charles Walker, a political unknown who has devoted neither time nor much money to defeating him, Cardin is in as good a position as any candidate could hope to be. And as the representative of a district that is overwhelmingly Democratic, he feels little threat from the field of four candidates vying for the Republican Party's nomination at the polls next Tuesday.

The Republicans are Ross Z. Pierpont, Frederic Parker, Douglas Harris and Roy F. Carraher. All of the candidates are from Baltimore or Baltimore County except Parker, who lives in Columbia.

Cardin is blessed with an incumbent's advantage and with what political observers said is a level of popularity perhaps exceeded by only his predecessor, Sen. Barbara Mikulski. Cardin, 43, said he has spent less than $10,000 on signs and newspaper advertisements for the March 8 primary. There have been no debates bringing him and his challenger together, and most of his campaign time has gone toward stumping for Rep. Richard Gephardt, Cardin's choice for his party's presidential nomination.

If there is a cloud darkening Cardin's optimistic outlook, it is the possibility that voters, confused by an earlier-than-usual primary or indifferent to their party's nominee, decide to stay home. For that reason, he plans to hold a campaign rally Sunday to make people aware of his race.

"There has been no primary interest in the congressional races," Cardin said. "I am confident if people show up and know that Congress is on the ballot, I will win."

Cardin's record in Congress includes support for legislation to reduce the trade deficit and clean up Chesapeake Bay. He has sponsored a bill to restructure the steel industry and supports a line-item veto for the president and a value-added tax.

Walker, 61, is a vice president of a Baltimore building company who, in opposing Cardin, is waging his first campaign for elective office.

If elected, Walker said he would work to penalize manufacturers who take their factories overseas to avoid working with labor unions by making them pay higher taxes, and encourage merchants to "sell American" by ensuring that they get to keep a higher share of profits.

He also supports capital punishment for all convicted murderers and a quarantine for people suffering from AIDS.

Among the Republicans, much of the attention has centered on Pierpont, 70, a retired Baltimore surgeon who garnered about 20 percent of the vote when he ran against Cardin two years ago.

Pierpont, who is waging his ninth campaign for elective office, has received the endorsements of the Baltimore Republican Central Committee and most major Republican clubs.

Pierpont said that if elected, he would pressure the Justice Department to investigate more fully the circumstances that led to Maryland's savings and loan crisis, which he claims have been covered up to avoid embarrassing several politicians still in office. He also advocates reducing the federal deficit by giving the president a line-item veto, instituting a value-added tax, and passing a balanced budget amendment.

Parker, 27, is an electrical engineer. The primary is his first campaign for elective office, and although he has been campaigning "pretty inactively," Parker said the experience has given him an opportunity to learn the process and introduce himself to voters. He declined to participate in the Republican Party's sole debate of the campaign season.

Among the changes he would advocate if he were elected are privitizing Social Security and curbing federal spending to reduce the deficit.

Harris, 41, the owner of a private detective agency in Baltimore, is also running in the Republican primary, but was out of town this week and could not be reached for comment. His campaign manager, Jewel Cummins, said Harris has not distributed campaign literature or done much campaigning outside of a few party functions, but is hoping he will be able to defeat Pierpont by attracting voters who are eager for a change. He supports women's rights to abortions and proposes a $1 check-off box on income tax forms to raise money for AIDS research, Cummins said.

The fourth Republican candidate, Carraher, could not be reached for comment.