After the American Lawyer magazine looked at the legal services program in New Haven, Conn., it suggested that President Reagan and others arguing that many government social programs were a waste of money should "send a hit squad" out after Bruce A. Morrison.

"Morrison runs a government-funded do-gooder program begun in the heyday of the Great Society," wrote author Steven Brill. "It works . . . . He may be the best bargain the taxpayers have ever had."

Reagan won't have to go to New Haven to see Morrison in action. The 38-year-old lawyer is on his way to Washington representing the 3rd District. In an election full of surprises, he provided one of the biggest. Morrison upset freshman Republican Lawrence J. DeNardis, a leader of the gypsy moths and, according to officials from both parties, an incumbent who ran little risk of defeat.

Using a network of volunteers and the support of labor, women and minorities, Morrison first upset the president of the New Haven Board of Aldermen in the Democratic primary in September. He then attacked DeNardis for supporting President Reagan's economic program, made Social Security and the nuclear freeze central issues, and characterized DeNardis as a politician who had flipflopped on key votes.

Morrison, who holds degrees in chemistry from the Massachusetts Institute of Technology and the University of Illinois and a law degree from Yale University, enjoyed overwhelming support of an active Democratic organization during the fall campaign.

Morrison said the Reagan administration's solutions to the country's economic programs "not only are failing to resolve those problems but are undermining the nation's commitment to justice, compassion, equality and opportunity."