District of Columbia voters are expected to turn out in record numbers to deliver what may be one of Democrat Walter F. Mondale's few electoral vote victories over President Reagan in Tuesday's presidential election.

But clearly the major contest in the D.C. election, and the race that has left much of the political community nervously guessing, is for one of two at-large City Council seats that are on the line.

City Council member Jerry A. Moore Jr. (R-At-Large), who was crushed by former school board member Carol Schwartz in the Republican primary, has been politically resurrected with an unusual write-in campaign that has the support of the city's Baptist ministers and much of Mayor Marion Barry's potent Democratic organization.

However, Moore's effort will be hampered by the cumbersome and confusing nature of a write-in strategy and a persistent, labor-backed challenge by Statehood Party candidate Josephine Butler, a longtime community activist who will appeal to some of Moore's constituency.

Schwartz is hoping to slip by Moore and Butler with a hard-charging and well-organized campaign drawing much of its strength from Schwartz's home base in Ward 3, a predominantly white, middle-class area west of Rock Creek Park, as well as gentrified areas of wards 1, 2 and 6.

Two others running for the at-large seat are Brian Moore, an independent, and Maurice Jackson of the Communist Party.

Voters will elect two at-large council members from a field of six candidates, with the two top vote-getters winning the seats. Incumbent Democrat John Ray is expected to win one of those seats easily, leaving the other five candidates to slug it out for the other seat.

"I think Carol Schwartz is in a very good situation," said Ivanhoe Donaldson, chairman of the D.C. Democratic Committee. "It's a question of who's your second choice, assuming Ray is the first choice and assuming some drop-off in the vote" for the second at-large seat.

"The multiples here are unlimited," Donaldson said. "It all depends on how the vote breaks."

The D.C. Board of Elections and Ethics has predicted a record turnout of 200,000 voters, which would top the record of 198,597 in the 1964 presidential election and far exceed the 178,434 total in 1980.

D.C. Del. Walter E. Fauntroy is running unopposed for his eighth term in Congress. Fauntroy has spent much of the campaign working for the Mondale-Ferraro ticket and for candidates outside the District.

Along with the two at-large races, City Council members Charlene Drew Jarvis (D-Ward 4) and H.R. Crawford (D-Ward 7) are running unopposed, while council members John Wilson (D-Ward 2) and Wilhelmina J. Rolark (D-Ward 8) face modest opposition.

Rolark is being challenged by school board member R. Calvin Lockridge, a Democrat who lost in the primary but who will appear on Tuesday's ballot as a Statehood and Republican candidate. Tom Kelly, a little-known Republican, is challenging Wilson.

Voters also will decide whether to approve Initiative 17, to give homeless people the right to overnight shelter and to require the D.C. government to provide it. City officials have opposed the measure, arguing that it would be too expensive to carry out and that it would encourage homeless people around the country to flock to Washington.

About 80 percent of the District's 274,810 registered voters are Democrats, and Mondale is expected to win the city's three electoral votes handily. Political observers say Mondale probably will match President Carter's take of 75 percent of the vote in the District in the 1980 election.

Yet, clearly, the thrill of presidential politics in this 70 percent black city dissipated after the May 1 D.C. presidential primary, which Jesse L. Jackson won with 67 percent of the vote.

Since then, Barry and other Jackson supporters have dutifully lined up behind Mondale. But there has been little noticeable campaign activity or hoopla, save a "Countdown to Victory" party at the Capital Hilton last Tuesday night that attracted 300 supporters and raised more than $50,000.

"Mondale and Ferraro will carry the District easily," Barry said at the party. "We're not working hard at it, either."

But many of Barry's staunch supporters are working hard to keep Jerry Moore in office. Moore, a Baptist minister and a 15-year council veteran, has developed close ties with Barry and has been endorsed by six Democrats on the council.

The mayor endorsed Moore in the Republican primary but since has adopted a neutral stand publicly, though much of his political organization eventually rallied to help Moore mount a write-in campaign that appears to be picking up steam.

The key to victory for Moore, who is black, is a large and enthusiastic turnout in wards 4, 5 and 7, the heart of the District's middle-class black community, and a dogged effort by campaign workers at the polls to explain to voters how to write in or stamp Moore's name on the ballot. Moore also has the backing of hundreds of ministers and church members.

"It would take a great machine to pull off a write-in campaign, but I don't put anything past anyone," said Sharon Pratt Dixon, the D.C. Democratic National Committeewoman.

Schwartz, a two-term former school board member, has run a highly visible campaign through the use of brightly colored posters, mass mailings of campaign literature and some radio advertisements.

Schwartz, who is white, beat Moore in the Republican primary with 57 percent of the vote and since then has attempted to broaden her base with an appeal to Democratic voters, while playing down her GOP affiliation.

D.C. Council member Betty Ann Kane (D-At-Large), who lives on Capitol Hill and has strong citywide support, is vigorously campaigning for Schwartz.

"I would give Schwartz the edge," said Matthew Watson, former city auditor and a local attorney who studies District voting trends. "There will be a heavy turnout in Ward 3 and she will get a substantial vote in the gentrified areas in wards 1, 2 and 6."

Butler, the Statehood Party candidate, describes herself as the "people's candidate." At a get-out-the vote rally yesterday on Western Plaza, across from the District Building, Butler said she will draw support "from whites and blacks, the old and young, and Democrats and Republicans."

Butler has drawn the support of every major Washington area labor organization and will benefit from labor's election day get-out-the-vote effort. The election may provide the clearest test yet of organized labor's political clout here.