Democratic canidate Steny H. Hoyer appears to have maintained the lead he began with in suburban Maryland's special congressional campaign, despite an intense effort by local and national Republicans to capture the 5th District seat in Prince George's County and thus strike another blow for President Reagan and his economic policies.

Hoyer aides said that their final analysis of telephone surveys and canvassing indicated that the 41-year-old former Maryland Senate president should defeat Republican candidate Audrey Scott by as much as 10 percentage points if registered Democrats vote in expected numbers this Tuesday. Scott's campaign managers, however, said that their candidate was rapidly closing the gap last week and still has a chance to pull off an upset.

"Our line is on the upswing and his on the descent," said Scott spokesman Jim McAvoy. "It's a matter of whether there's enough time by election day." Hoyer campaign manager John McDonough said, "By every indice I know of, we've got it. They've lost it, lost control. They're not closing the gap, it's widening. The only thing I worry about is complacency."

Scott, considered the underdog throughout the six-week race to fill out ailing Gladys Spellman's term in Congress, has sought to overcome that status by aligning herself with Reagan and his personal popularity. She has received financial and other assistance from the national Republican Party, which hopes that this election will slim the Democaratic majority in the House of Representatives and demonstrate that the GOP still has the momentum that began with the 1980 election.

And as a sign of the seriousness with which the GOP leadership views this election being waged just a few miles from the White House, the Scott campaign in the last few days has begun extensive airing of a television endorsement by Vice President Bush and has sent thousands of undecided voters personal letters of endorsement signed by President Reagan.

However, because of the district's 3-to-1 Democratic registration, the comfortable margin the district, dominated by federal workers, gave Jimmy Carter in the 1980 presidential election, and the mixed feelings expressed toward many Reagan proposals in polls by both candidates, the GOP leaders have generally avoided calling the race a referendum on Reagan's policies.

Despite the disclaimers about the race's national implications, the campaigns waged by Scott, Hoyer, and to a lesser extent, Libertarian candidate Tom Mathers, have centered on the effect of the Reagan proposals, with Hoyer endorsing the more moderate Democratic alternatives and Scott backing the Reagan package. As a result, when the voters go to the polls May 19 they will in part be casting a ballot based on their perception of the administration's programs.

Said Maryland Republican Party Chairman Allan C. Levey: "Unless someone has a strong feeling for Audrey or a strong feeling for Steny, they're going to vote for or against Reagan."

And the two national parties, despite their initial disclaimers, expect Reagan to be very much a part of post-election analyses. "The day after the election, whoever wins will clearly declare that this was a great victory for their side," said Ann Lewis, political director of the Democratic National Committee, which has been actively involved in the Hoyer campaign.

But as important as national political concerns have been, the special election to fill out the term of former congresswoman Spellman is also a race between two individuals and the voters' perceptions of them.

On one side is Hoyer, the polished, former Maryland Senate leader who, having lost his bid for lieutenant govenor in 1978, is hoping in this election to make a political comeback. Hoyer has sought to emphasize his 15 years of experience in government, which he began as a 26-year-old state senator, and his acknowledged leadership abilities.

On the other side is Scott, 45, the mayor of Bowie, who has sought to portray herself as a civic activist much in the style of the early career of the popular Spellman. With less experience than Hoyer, Scott has concentrated on her desire to perform constituent services as she has done in Bowie.

But, because Prince George's is so Democratic -- only one Republican has won election in the last seven years and Scott herself has lost in two bids for the state legislature -- Scott turned much of her campaign effort toward wooing Democrats who might be disenchanged with Hoyer. She has done that, primarily, by calling Hoyer a "big spender" and "machine politican" and by running a series of advertisements attacking his record.

These ads, however, seemed to have caused Scott some problems of her own. Many Democrats criticized her for running a negative campaign; Scott became somewhat defensive; the chairman of the Hoyer campaign held a widely publicized press conference denouncing her "dirty tricks," and her campaign staff spent time and energy arguing over the ads.

The squabble over the television advertisements was only one of a few such issues to come up in the campaign. When the race first began after a crowded primary election on April 7, Scott accused Hoyer of improper behavior by his decision to stay on a politically sensitive County Council redistricting committee while a candidate for office. After others criticized Hoyer, he quickly submitted a letter of resignation effective May 20.

Both candidates initially suffered from splits within their own parties caused by unusually large and bitter primaries. A week after the primary, a group of Democrats expressed reservations about Hoyer's candidacy because of worries that he would reinvolve himself in local politics. Some of those Democrats have since gotten involved in the Hoyer campaign but others have continued to remain aloof.

On the Republican side, Scott spent much of her primary race vigorously attacking her main primary opponent, Lawrence Hogan Jr., and his father, the powerful and popular county executive. Since the primary, neither Hogan has done much to help her campaign. The senior Hogan, after saying nothing for the first five weeks of the general election campaign, issued a belated and lukewarm endorsement of Scott a few days ago.

But as much as these charges and countercharges distracted the candidates, the two campaigns have been focusing on the much more raditional election activities of gathering money and pledges of support.

In addition to endorsements from well-known Democrats, the Hoyer camp lined up support in areas where Scott was considered to have strength: women, business and municipal officials. Scott spent much of the first weeks of the campaign attempting to win the backing of well-known Democrats. In the end that effort failed, and Scott concentrated instead on garnering endorsements from a host of state and national Republican politicians, many of whom came into the county this week to stump for her.

She was able to stay even with Hoyer in getting contributions. By the end of last week Scott had raised a total of $212,000 for the general election and spent almost all of it, with a large amount going for television advertisements needed to increase her name recognition. Since Spellman's seat was first declared vacant last February, Scott has raised $244,000.

Hoyer raised and was expected to spend $176,000. With primary race contributions included, Hoyer has raised a total of nearly $300,000. Only 25 percent of Hoyer's general election budget went for television time. The Hoyer campaign concentrated instead on mailing brochures and calling voters by telephone.

By Friday, the Hoyer campaign had contacted about 25,000 voters who said they supported him, and the Scott campaign had identified about 15,000 supporters. Both sides expect about half of the 173,196 voters in the district to turn out Tuesday. The polls will be open from 7 in the morning to 8 p.m. and the final results will be known by 10:30 p.m., according to county election officials