Candidates representing both “new” and “old” Boston vaulted past three rivals in a preliminary election that winnowed the field for this November’s Boston City Council election.

The results set up a race that pits Gregory J. Glennon, a 32-year-old prosecutor, against Mark S. Ciommo, a lifelong resident who received the backing of 10 of Boston’s labor unions.

The outcome of the November election is of particular importance to Harvard because of the University’s plans to construct a new campus in Allston. The councillor who represents the Boston neighborhood will be a key negotiator on behalf of local residents.

With 100 percent of precincts reporting, Ciommo won 31 percent of the vote to Glennon’s 28 percent. Brighton attorney Timothy N. Schofield, who had raised the most campaign funds, placed third with 21 percent.

Ciommo, 50, has served as executive director of a city-run senior center in Brighton for the past 14 years. Throughout the campaign, he emphasized his working-class roots, noting that he was raised by a single mother and was the first person in his family to earn a college degree.

Glennon, an assistant district attorney who has lived in Brighton for a decade, has a longer history of political activism. He ran for state representative in 2005, and served for years as legal counsel to former state Rep. Brian P. Golden, a Democrat who gained notoriety for endorsing President George W. Bush in 2004.

Yesterday’s preliminary election lacked the excitement of a race for Boston’s four at-large seats—which are elected city-wide along with the nine seats that are elected by districts. Because nine candidates are running for the at-large seats and a preliminary would have only reduced the number to eight, officials cancelled a city-wide preliminary, deeming it wasteful.

-Staff writer Paras D. Bhayani can be reached at pbhayani@fas.harvard.edu.