His 15-year tenure in the House ending a shaken Fred B. Rooney arrived in the offices of his district's largest newspaper, the Allentown Call-Chronicle, where the biennial ritual of the election-night returns was being telecast.

The 53-year-old Democrat from nearby Bethlehem had been one of 19 incumbent U.S. representatives defeated Tuesday, in what was among the most surprising outcomes in the Northeast and one of a handful of unanticipated losses for veteran incumbents.

Not one political observer here had predicted Rooney's downfall in his race with Donald L. Ritter, a 38-year-old conservative Republican who had taken leave as a research director at Lehigh University to try what had seemed to be a futile run at Rooney.

National observers have remarked that no major figures in the House were beaten on Tuesday, and several national reporters have referred to Rooney as "obsecure," but you couldn't say that here in the pleasant, rolling hills of the Lehigh Valley. Rooney also has been important to railroad interests as chairman of the House Commerce transportation subcommittee, where he had earned a reputation of afirness among both management and union rail lobbyists. Rooney was a major architect of legistation of fairness among both man-other railroad bills, including Amtrak authorization measures.

Rooney had never lost an election. After two terms in the Pennsylvania Senate, the moderately Liberal law-maker won a 1963 special election to the 15th Congressional District seat that had been held by the late Francis Walter, a conservative who had made his reputation as a tough interrogator on the old House Un-American Activities Committee.

Rooney won seven straight terms after that, only once having a close call - a 52 percent victory over a respected Republican foe in 1966.

No one ran aganist him in 1974. Two years later, an unknown salesman dropped out after winning the GOP primary when he was offered a job outside the district. Rooney clobbered a hastily recruited novice in the general election with 65 percent of the vote.

By this spring, the local Republican parties were running newspaper advertisements plaintively asking candidates to take on Rooney. Up until then the National Republican Congressional Committee had planned to "target" Rooney for defeat. Although committee strategists had thought Rooney might be weak after having no competition, they waivered when on strong candidate seemed to surface. When an unknown, but eager and fairly articulate Ritter won the GOP primary in May over five rivals who answered the newspaper ads, the committee changed its mind.

Five months later, Fred Rooney trudged into the newspaper office, a beaten man. The final tally wasn't even close: Ritter 65,796, Rooney 58,001.

"Well, you won't have me to worry about anymore," he told a reporter before going on camera.

Bearing up, Rooney told his television audience that he was "chagrined." He blamed his defeat primarily on Ritter's sterotyped campaign against high taxes and big government, something Ritter had said Rooney had stood for. By other accounts, the records for Rooney's loss were less ideological than that.

People at home suddenly realized their Congressman hadn't been around much in recent years.

Lack of opposition in 1974 and weak resistance in 1976 had left Rooney's stumping skills rusty, short weekend trips home dwindled to once a month. While Rooney stayed in Washington this year, preoccupied with his railroad constituency and leading a well-ensconced family life with his wife and three children, Ritter was everywhere in the two-county district. Often almost ignored. Ritter still hit the circuit, attending the picnics, the banquests, the out-of-way local meetings.

State Senate Majority Leader Henry Messinger summed it up for many Democrats in Lehigh and Northampton counties:

"Fred didn't pay any attention to home. He rarely came up to events in the county anymore. He always sent telegrams.

To be sure, there were other factors contributing to Rooney's sudden inability to take advantage of a voter registration edge of 45,000 Democrats. While more than 95 percent of congressional incumbents were again being reelected, Rooney had failed to carry home precinct in Bethlehem by 107 votes.

The most obvious was Democratic gabernatorial candidate Pete Fisherty's failure at the top of the ticket. Victorious Republican Richard Thornbury took the 15th District here by more than 17,000 votes. Local party leaders complained that the once-favored Flaherty organisation had provided no help at the local level. The resulting drain was felt by the area's normally popular Democratic state legislative candidates, including Messinger, who was reelected by about 1,500 votes - far less than his usual margin.

But Rooney had run well before in strong Republican years.

Party officials, his aides and Rooney himself had also smarted over the first recurrent dose of negative publicity in his career. Most of it, over the last three years, concerned the growing amount of special interest campaign contributions he received since he became chairman of the transportation subcommittee in 1975.

Rooney's reelection committee had attracted a record $96,000 this year. That was double Ritter's campaign war chest, which was helped considerably by $13,000 from Republican committees. With railroad unions and management political action committees leading the way, three-fourths of Rooney's support came from special interests. The congressman was on recording in favor of public financing of elections, but said he would use the current system until the law could be changed.

News stories reporting the extensive family-inherited wealth of his wife, Evelyn, also embittered Rooney. Financial disclosure statements required by House ethics rules in 1977 showed Mrs. Rooney held an investment port-folio worth a minimum of $150,000. Admittedly to conceal the more precise nature and amount of her holdings. Rooney's accountant put at least $100,000 of her investments in a blind trust this year.

The stocks were held by his wife, and Rooney said the stories made it look like he was "one of the richest members." Insofar as it applied to spouses of members, Rooney labeled the required disclosure "an invasion of privacy."

He was never able, during the congressional wave of reform in recent years, to concede there was a potential of conflict between some of his legislative actions, the large campaign contributions or his wife's holdings.

There were recurrent rumors about Rooney's health, although tests at Bethesda Naval Hospital this year had reportedly confirmed successful treatments for thyroid cancer. Most observers continued to notice a shaking or palsy of Rooney's hands at public appearances, something sources close to him attributed to nervousness.

Finally, Ritter's bare-bones, but effective media campaign attacked Rooney's record where it hurt the most - the congressman's handling of bills funding the deficit-ridden Conrail. Ritter claimed Conrail, the Northeast freight carrier subsidized by federal investments Rooney's subcommittee, had helped devise, should be de-centralized to make it more efficient. Rooney replied that Ritter had no real expertise, that Conrail "was the only game in town."

The Interstate Commerce Commission provided initial embarrassment in June, announcing a proposed $2.3 million fine against Conrail for failure to move freight cars promptly.Half the violations occurred at the Council Allentown yards in Rooney's district. Ritter demanded oversight hearings, which Rooney eventually held in Washington, saying he had planned to do so all along.