Campaign managers for both Mayor John B. Hynes and his opponent, State Senator John E. Powers, were optimistic last night about their candidates' chances in the biggest of today's local elections. The polls open at 8 a.m., and close at 8 p.m.

Late yesterday, Marty Ryan, Hynes' manager, said that with a large vote-- 175,000 to 180,000--Hynes would "positively be elected, since the people realize that it is necessary to vote for John Hynes if they want good city government." He did not believe that rate would reduce the chances of such a large turnout.

At Powers' headquarters, however, Manager John Fitzgerald, Jr. contradicted newspaper predictions that a heavy vote would mean reelection for Hynes. "Newspapers don't vote," he asserted. "They're pushing Hynes, but the people are for Powers. We're going to slaughter Hynes."

In Cambridge, meanwhile, the Civic Association also predicted victory for its candidates. Russell Peck, CCA publicity director, said, "we have high hopes for success. We expect to get at least six out of nine candidates on the City Council and four out of six on the School Committee." The Cambridge results will not be known for at least a week, he pointed out, because of the proportional representation voting system.

Judson T. Shaplin '42, assistant professor of Education and candidate for the Cambridge School Committee, was less optimistic about his chances, saying that "it will be a very close fight, but I have a fairly good chance to be reelected. More people know me than two years ago, when I first ran."