The five Montgomery County Democrats competing for Maryland's 8th District congressional seat made their first joint appearance of the campaign last night, offering voters vastly different personal and political records but few substantive differences on issues.

The candidates -- state Sen. Stewart Bainum Jr., lobbyists Leon Billings and Wendell M. Holloway, County Council member Esther P. Gelman, and former representative Carlton R. Sickles, spoke on issues as diverse as tax reform and terrorism with a mutual low-key style that some Democrats doubt will survive a grueling six-month primary campaign.

Not surprisingly, each candidate claimed to be the best qualified to succeed Democratic Rep. Michael D. Barnes, who is leaving the House to run for the U.S. Senate. Republicans Constance A. Morella, a state delegate from Bethesda, and retired foreign service officer William S. Shepard will compete for nomination in the Republican primary.

Bainum and Gelman stressed their years in state and local government, while Billings, Holloway and Sickles emphasized their various careers on Capitol Hill.

"Some people have told me I was a damn good congressman," said Sickles, who served in Congress for four years in the 1960s. "I'm still very much in this race."

All five candidates, in brief speeches to about 50 members of a Democratic club in Gaithersburg, sounded similar themes on U.S. involvement in Latin America, national tax reform and methods to combat terrorism against Americans abroad.

Where they differed most was in the presentation of their political resumes, career records they said best reflected the generally affluent and fast changing electoral district, which consists of most of Montgomery County.

"Where else but in Montgomery County would you have this array of candidates?" said Del. Gene Counihan, who represents the Gaithersburg area in the General Assembly. "They are not that far apart on the issues but they come to this race from totally different backgrounds and personal experience."

Billings, who was the most animated of the five despite a cold that left him with practically no voice, differed sharply from the other candidates by flatly opposing any U.S. aid to the contras in Nicaragua and with an assertion that he would have voted against the tax reform measure that has passed the House of Representatives.

Holloway, a lobbyist for the Ford Motor Co., echoed the views of the other four candidates when he called for a "strong but cost-effective" U.S. defense.

Holloway's message appealed to Josephine Wang, a Republican precinct chairman who attended the candidates forum. "I like Wendell because he is conservative on defense, but I think Esther Gelman is very good -- she's a human interest candidate" said Wang.

Mickey Sohn, a 48-year-old Gaithersburg man who said he is not affiliated with any major political party, said the candidates' exchange persuaded him to support Holloway.

Sohn said he admired Holloway's candor and said "he was straightforward and has a good background."

"Come the primary, I'll probably support him," Sohn added. "But it's a long time till then, you never know what could happen."