Boston — For the first time in more than a decade, Massachusetts Republican leaders are optimistically scanning the electoral horizon. * In the race for the United States Senate seat of retiring Democrat Paul E. Tsongas, polls now show that Elliot L. Richardson is ahead of all four of his Democratic contenders, including Lt. Gov. John F. Kerry and US Rep. James N. Shannon, as well as his GOP opponent, Raymond Shamie.
* At least one and perhaps two US House seats currently held by Bay State Democrats may also be within Republican reach.
In the 10th District, a considerable Republican effort can be expected for the seat of six-term Democratic US Rep. Gerry E. Studds, who was censured in 1983 by his House colleagues for a 1973 homosexual affair with a 17-year-old congressional page.
Also particularly promising to the GOP, whose congressional ranks have thinned from six to one in the past 14 years, is the Fifth District seat being vacated by Representative Shannon.
Mr. Studds faces a tough battle in the Sept. 18 Democratic primary. It is still uncertain to what extent the misconduct censure may weaken his prospects, despite efforts by his chief Democratic opponent, Plymouth County Sheriff Peter Y. Flynn, to focus on it. Sixty-five percent of those questioned in a random poll within the district in late June by the Quincy Patriot Ledger said the Studds censure would not be a factor in their decision in the election.
The incumbent's potential vulnerability has attracted three GOP challengers. The leading contender appears to be Lewis Crampton, a former state commissioner of community affairs and the party's 1978 nominee for state treasurer. Until recently he was a high-ranking official in the federal Environmental Protection Agency.
The 10th District, a one-time Republican stronghold that includes the state's South Shore and Cape Cod areas, was wrested from the GOP by Studds, a liberal, in 1972.
Although Democrats outnumber Republicans in the district, the margin is slimmer than in most of the other 10 Massachusetts congressional districts, notes Gene Hartigan, executive director of the Republican state committee.
The fierce Studds-Flynn primary contest could make it difficult for Democrats to close ranks behind a nominee, thus perhaps indirectly boosting Republican prospects in November.
State GOP strategists also hope to benefit from a hard-fought Democratic battle for the Shannon seat in the Fifth District, which until 10 years ago had been a Republican bastion for decades. Squaring off in the primary are state Sens. Chester G. Atkins, a Concord liberal, and Philip L. Shea, a Lowell conservative. As state Democratic chairman for the past five years, Mr. Atkins is probably better known in the district. Mr. Shea, on the other hand, is from the Merrimack Valley, from whence the district's congressmen have generally come.
Republican are pinning their hopes for winning back the Shannon seat on Gregory Hyatt, a ballot newcomer, and former executive director of Citizens for Limited Taxation, the group that spearheaded Proposition 21/2, the 1980 ballot initiative that rolled back property taxes across Massachusetts.
Meanwhile, Silvio O. Conte, the state's only GOP congressman, is expected to have no difficulty in winning a 14th term.