Today, primary day. Gov. Michael S. Dukakis and Sen. Edward W. Brooke (R-Mass.) are up for re-election, and for the first time in three decades, three of the twelve congressional seats are vacant.

Five Democrats and two Republicans are contesting Brooke's seat. Coming up on the right is Republican candidate Avi Nelson with a well-financed and well-organized campaign.

Incumbents Dukakis and Brooke, both facing formidable opponents, hope for a large voter turnout, but predicted bad weather is expected to reduce the crowds at the polls.

The battle for seats in the state House of Representatives will be particularly fierce this year because only 160, instead of the previous 240, will be elected this year.

Interesting Congressional races include the Democratic primary in the Eleventh District, which--as the Republicans are unlikely to run their own candidate in November--will decide the issue immediately.

If Republican candidate Lois Pines wins the Democratic nomination for secretary of state, she will be the first female candidate endorsed by a major party in Massachusetts for state-wide office since 1970. Should she beat Republican John Sears, she will be the first woman to hold a constitutional office at the state-wide level.

The Boston Globe reported most incumbents in other states survived the primary elections but some professional politicians believe the Red Sox' slump may make voters seek a change in political race.