A poll released by Republican Audrey Scott yesterday shows Democrat Steny Hoyer with a comfortable but not overwhelming six-point lead in Maryland's 5th Congressional District race, indicating that next month's election for the seat could be closer than expected.

The poll, the first made public since Scott and Hoyer won special primary elections April 7, also shows surprising support for President Reagan and national Republican policies among both Democratic and Republican voters in the district, which encompasses northern Prince George's County and a sliver of Montgomery County. Those supporters include federal employes likely to be most affected by the cutbacks proposed by the Reagan administration.

The results surprised members of both parties, who said they assumed the May 19 election to fill the seat left vacant by Gladys Noon Spellman would be an easy victory for Hoyer and the Democrats in a county that voted overwhelmingly for Jimmy Carter in 1980.

Officials of both the Scott campaign and the national Republican party said they now believe it is possible for Scott to surge ahead and win the seat that Republicans held just seven years ago.

According to the poll, based on telephone interviews with 302 registered voters, 47 percent of the voters surveyed say they will support Hoyer, the former Maryland Senate president, and 41 percent indicate support for Scott, the mayor of Bowie. Another 12 percent of the voters polled said they were undecided about which candidate to vote for.

The poll, conducted by Detroit-based Market Opinion Research, one of the premiere Republicans polling firms, was conducted on April 9 and 10, soon after Scott won an upset victory in the Republican primary and Hoyer emerged the victor in a fractious 19-candidate Democratic race.

Scott's campaign staff members said they are elated by the results of the survey. They expected Hoyer to have a much larger edge, considering the Democrats' three-to-one edge in registration in the district.

"This is no uphill fight," said Scott press aide Jim McAvoy. "This is a classic situation where the Democratic frontrunner will be scampering around holding on and the Republican will steadily gain. If I were Hoyer I'd be damned scared."

Hoyer campaign manager John McDonough said the results of the poll did not disturb or surprise him, in part because the poll has a nearly 6 percent margin of error that could substantially increase Hoyer's share of the vote to 50 percent and drop Scott under 40 percent.

"We're perfectly content to rest on their poll, which shows us ahead. I think we're more ahead [than Scott's polls indicates]. A Republican pollster would tend to make it look closer and a Democratic pollster would make it look farther apart."

In addition, the poll results could be somewhat shewed in favor of Scott and against Hoyer by a sampling that may have underestimated the percentage of black voters, a group expected to come out strongly for Hoyer.

Only 16 percent of the 302 voters surveyed were black, although blacks represent about 40 percent of the Prince George's population, though a smaller percentage of registered voters. "It's possible that [the poll] misstates or understates the black vote which would mean [it] understates Hoyer," said one pollster associated with the Scott campaign.

The poll shows that Scott has the strong support of Republican voters surveyed, a finding in keeping with her overwhelming victory in the 12-person GOP primary. Hoyer, on the other hand, apparently suffers from the party's hotly contested primary that pitted strong factions against each other and resulted in some bitterness. About one-third of those surveyed who had voted in the Democratic primary said they would support Scott instead of their party's choice.

The poll also indicates that Hoyer has a decided advantage in being better known in all parts of the county -- 88 percent of those surveyed recognized his name. Scott had high name recognition in her hometown of Bowie but was not well known in other areas of the county. Only 68 percent of those called recognized her name.

The survey also suggests that many voters are supporting Hoyer over Scott because of his greater experience in government and politics. Hoyer served in the state Senate for 12 years, was Senate president and ran the Prince George's County Democratic party; Scott has been mayor of Bowie for six years but has never served in state or county government.

Only a small percentage of voters indicated they would not support Hoyer because he lives outside the district -- by four blacks -- or because he has long been associated with the powerful Democratic organization that some have charged operated like a political machine. Scott intends to make both issues key points in her campaign.

When asked, "Do you favor or oppose President Reagan's economic plan?", 60 percent of those polled said they favor it, 30 percent said they oppose it and 10 percent said they were undecided.

Asked whether they had "more confidence in the policies and programs of the Republican Party or the Democratic Party in helping to solve the major problems facing the country?", 46 percent said the Republicans, 28 said the Democrats and 26 said they were unsure.