Less than 10 per cent of Massachusetts' 2.5 milion registered voters are expected to vote today in the state's complicated and expensive--but not significant--Presidential primary.

Experts believe that President Johnson and Ambassador Henry Cabot Lodge '21 will receive more votes than any other prospective Presidential candidates. Neither man's name appears on the ballot, however. The write-in vote will be only an expression of preference, moreover, and will not be binding upon delegates to the parties' national conventions this summer.

The most interesting race promises to be among delegates to the Democratic convention, even though all 56 candidates are running unopposed. Sen. Edward M. Kennedy '54, Attorney General Robert F. Kennedy '48, Governor Endicott Peabody '42, and Mayor John F. Collins of Boston are among the names listed, and their votes will be watched as indications of political strength.

Robert Kennedy has been mentioned as a candidate for vice-President and most recently, for vice-President and most recently, for governor; Collins is reportedly considering running for governor or senator; and Peabody and Edward Kennedy are expected to seek second terms.

The choice for Republicans will be between rival slates of delegates pledged to Senator Goldwater and Ambassador Lodge. (No slate is committed to Governor Rockefeller.) Although no delegate is listed as pro-Goldwater or pro-Lodge on the ballot, certain names--like that of Lodge's son, George C. Lodge '50--will tell knowledgeable voters which slate to select. Thirty-four delegates will be elected to represent the state's Republican minority.