Walter F. Mondale's strong showing against President Reagan in the presidential campaign debate in Louisville over the weekend provided a much-needed boost in morale for the District's Mondale supporters in the District, who now think their candidate stands a chance.

"I think we have a real race now," said City Council member Charlene Drew Jarvis (D-Ward 4), a national vice chairwoman of the Mondale-Ferraro campaign. "I think that he countered the perception of a problem with leadership. . . . He Mondale knows where he's going and what he wants to do."

Mayor Marion Barry, who took charge of Mondale's local campaign effort after vigorously backing Jesse L. Jackson during the primaries, said that he was "very surprised" by how well Mondale did. "He was very strong, very relaxed," Barry said. "He wasn't uptight."

The mayor pooh-poohed the importance of Mondale's poor showing in recent national polls and predicted that the former vice president would somehow pull out a victory in November.

"It's going to be the enthusiasm of the black people that's going to be the margin," Barry said. " . . . Be wary and leery of these polls."

Mondale's crisp and often pointed delivery was praised by other D.C. supporters, who had begun to fear that the voters were being lulled to sleep by Mondale's lethargic general election campaigning.

The small group of Democrats who attended a $50-a-ticket Mondale fund-raiser at the Convention Center Sunday night to view the televised debate cheered and applauded frequently as Mondale scored points. Many in this partisan crowd commented that Reagan, "the Great Communicator," at times seemed tentative or confused.

"I thought Reagan did terribly," said Pauline Schneider, the mayor's director of intergovernmental relations and a former Carter administration official. "He really wasn't very coherent. . . . It really was shocking. Maybe it was beyond his bedtime."

Another Democrat who attended the fund-raiser quipped that Reagan does not do very well without a script.

"But it's not important what we say about it," he added. "What's important is what the news commentators say in the next 48 hours."

Jarvis, who hosted a debate party in Ward 4 that drew about 75 people, said that until now the press has greatly influenced the public's perception of the presidential race and that Mondale has not faired well.

"Sunday night was an opportunity to see directly the leadership style of Mondale," said Jarvis. " . . . I think people will now begin to listen much more carefully to the two candiates and will focus much more on substance than on style as a result of the debate."

The Democratic State Committee elected 12 ex-officio members at its meeting last Thursday.

The six additional men chosen were James Mercer (Ward 1), Bernard Demczuk and Steve Ramirez (Ward 2), Walter Beach (Ward 3), James Christian (Ward 4) and Andrew P. Corley (Ward 5).

The six women elected were Myrna Peralta-Guevara (Ward 1), Irene Lee and Emma Patton (Ward 2), Barbara Bell Clark and Florence Pendleton (Ward 5) and Winifred Freeman (Ward 8).

The party will hold an election among Ward 8 Democrats in November to fill a vacancy left by D.C. school board member R. Calvin Lockridge after he decided to run as the Republican and Statehood nominee in the general election race for the Ward 8 City Council seat.