FOLLOWING his primary election upset of Gov. Michael S. Dukakis (D), Edward J. King (D), 53, was hit by twin troubles: massive liberal Democratic defections, caused by the hard-line social and fiscal stands he took in the primary, and heavy publicity on his free-spending habits as former director of the Masachusetts Port Authority. Inside a month, he lost his 20-point led over state House minority leader Francis W. Hatch Jr. (R), 53, his blueblood Yankee moderate opponent. But the Hatch campaign has been erratic, labor has backed King, and Lt. Gov. Thomas P. O'Neill III, (D) and his father, the House speaker, are pressuring organization Democrats to stay in line for the King-O'Neill ticket. King is stressing his party label and traditional Democratic concerns for jobs and cities, and probably has a chance to pull out a victory despite private polls showing Hatch with a small lead.

Sen. Edward W. Brooke (R), 59, seeking a third term, survived a serious primary challenge from conservative Avi Nelson only to ride into yet another confrontation with the Senate Ethics Committee over the complex financial arrangements revealed during his divorce trial. Meantime, his opponent, Rep. Paul E. Tsongas (D), 37, used the momentum of his own primary victory to move into a clear but narrow 6-to-10 point lead. However, Brooke, the Senate's only black member, is also one of its most gifted campaigners, and in liberal Massachusetts that combination may yet allow him to fend off what has seemed a likely defeat.

Republicans are challenging hard in Tsongas' old House district and that of retiring Rep. Michael J. Harrington (D), but Democrats are favored in the latter and have at least an even chance in the former.