BROOKLINE, Mass. — Days after Joseph P. Kennedy III stood in front of the Democratic National Convention to offer a tribute to his great-uncle, Senator Edward M. Kennedy, he found himself on a smaller platform just outside Boston, shaking hands with commuters at a public transit station here on the first day of his general election campaign in the Fourth Congressional District of Massachusetts.
Mr. Kennedy, 31, handily won his primary election Thursday, taking 90 percent of the vote in a contest with two relatively unknown rivals, Rachel Brown and Herb Robinson, and once again keeping the Kennedy name prominent in Massachusetts politics.
A former assistant district attorney and Peace Corps volunteer, Mr. Kennedy is hoping to take the seat occupied by Barney Frank, who announced last fall that he would retire after representing the district for more than 30 years.
“Those are very, very, very big shoes to fill,” said Bobbi Fox, 58, a software engineer who, like Mr. Frank, lives in Newton, Mass., and was chatting with Mr. Kennedy on Friday evening. She said that she planned to vote for Mr. Kennedy but that he still needed to prove himself to voters who probably knew more about his family than about him.
Mr. Kennedy’s challenger, Sean Bielat, shares the sentiment.
“Based on what I’ve seen from his résumé, it’s pretty thin,” said Mr. Bielat, who defeated Elizabeth Childs, a former state health commissioner, and David Steinhof, a dentist, in the Republican primary.
Mr. Bielat, 37, a businessman and a former Marine, ran an aggressive race against Mr. Frank in 2010.
