When a Democratic candidate for Congress issues a press release praising the fact that he did not get the endorsement of the AFL-CIO, it tells the casual voter something about the candidate, and perhaps more, about the district in which he is running.

That's the situation in the 1st Congressional District of Maryland, where Joseph D. Quinn, a certified public account with no prior political experience, is challenging three-term incumbent Rep. Robert E. Bauman (R-Md.), one of the best known, and from the Democratic point of view, least liked, members of the House.

Quinn, 35, has perceived that he cannot beat Bauman by attacking his conservative politics because his voting record apparently pleases the residents of the 13-county district that includes all of the Eastern Shore, southern Maryland and Harford County. So he has concentrated on criticizing Bauman for "how he spends his time."

Quinn sees his failure to win the endorsement of the state AFL-CIO as proof that "I am too conservative" for big labor, and therefore as much in step with the voters as Bauman.

Quinn says that Bauman's preoccupation with parliamentary procedures on the House floor, where he is the self-assigned "watchdog" for conservative interests, and his growing role as a national spokesman for right-wing causes, has deprived his constituents of his service on committees and the personal attention to individual problems.

"I will spend more time in the district," said Quinn. He sees a congressman's role as a "conduit" among local and state officials to bring the federal influence, and dollars, to bear on problems such as sewers, highways and fish hatcheries, to the court houses and statehouse.

Instead of being "an obstructionist" on the House floor, as he contends Bauman is, Quinn will "open up doors in Washington for local people, instead of slamming them, as Bob has done."

Although surveys commissioned by both Quinn and Bauman show the incumbent with a comfortable lead, Bauman is campaigning aggressively.

"In a district where Democrats out-number Republicans nearly 3 to 1, I can never take it easy," Bauman said the other day. "I'm up early and out late every day."

The rigors of Bauman's campaign are eased by the financial support he gets from conservatives across America. He will spend more than $125,000 defending his incumbency, and according to Quinn, 80 percent of that money will come from political action groups or right-wing individuals who live outside the district. By contrast, more than half of the $75,000 Quinn is spending has come out of his own pocket.

Bauman does not deny he gets lot of outside help - he has a personal mailing list of 15,000 persons with whom he communicates year-round - but he puts the percentage of outside contributors at closer to 50 percent.

Bauman also believes that Quinn's suggestion that he neglects his local constituents to play to a national audience "won't fly."

Bauman writes a weekly newsletter that is published by the dozens of small newspapers that dot the district, and he commutes to Washington daily from his home in Easton, so he has high visibility among his neigbors year-round.