Cambridge city residents cast their ballots at a Senior Citizens Center in Central Square yesterday evening. Yesterday’s voter turnout—slightly under 15,000—was the lowest in recent memory.

The Sullivan family dynasty, which has held a seat on the Cambridge City Council since 1936, is no more.

In yesterday’s elections, challenger Edward J. Sullivan Jr. lost a bid to replace his cousin, recently-retired Michael A. Sullivan, according to preliminary returns released last night.

Meanwhile, challenger Sam Seidel, a wonkish Harvard-trained urban planner coming off of a narrow loss in 2005, won a place on the council, and Councillor David P. Maher, who was elected in a special election in September, retained his seat.

Seidel was not in the room when his victory was announced at the Cambridge Senior Center shortly before midnight yesterday. He had stepped out for a drink at a Central Square tavern and was informed of his apparent victory by his wife, Ann Smith, who sprinted down the street to the bar, local reporters in tow.

“This is very exciting,” Seidel said with trademark calm and a beer in hand. “If the results hold up, I look forward to the real challenge we’ll have in moving the City Council forward.”

Seidel’s victory over Sullivan surprised political observers, who had predicted that Sullivan would win because of his family’s long history in Cambridge.

“I voted for Sullivan because I have supported the family for over 50 years,” said Benedict F. Fitzgerald, a 93-year-old who is a lifelong Cambridge resident, outside of the polling place at the Graduate School of Design’s Gund Hall.

Though support from voters like Fitzgerald appeared significant—Sullivan came in just behind Seidel—it was apparently not enough in the end.

All the other incumbents were reelected, with veteran Councillor Henrietta Davis winning the most votes.

In the race for the Cambridge School Committee, former committee member Marc C. McGovern—who was defeated for reelection in 2005—stormed back, winning the most votes of all the candidates.

Challenger Nancy Tauber won a seat, while veteran School Committee member Richard N. Harding Jr. lost. Cambridge’s school district, which is nearly two-thirds minority, will be governed by an all-white School Committee, if the preliminary returns hold.

The results did nothing to alter the balance on the renewal of Superintendent of Schools Thomas D. Fowler-Finn’s contract, which will be one of the committee’s first actions upon taking office.

Despite the retirement of Fowler-Finn supporter Nancy Walser, her protege, Tauber, won a seat. And though Harding, a critic of the superintendent, lost, McGovern, a fellow critic, won.

Yesterday’s election marked a 33 percent reduction in voter turnout over the past four years, with participation dipping below 15,000 for the first time in memory,

This year, successful city council candidates needed 1,344 votes to win, compared to 1,608 in 2005 and 2,009 in 2003.

Though the day’s foul weather may have put a damper on voter turnout, city residents attributed the overall trend of fewer voters to a combination of apathy among students and ignorance among residents.

“[Student] life is a mixture of parties and academics, and the affairs of the city don’t fit in very well,” Tom D. O’Leary, who has lived in Cambridge for 27 years, said at the Quincy House polling station. “As for the residents, it is only an abominable lack of consciousness that keeps them from the polls.”

Under Cambridge’s election system, known as “instant runoff voting,” residents rank their candidates in order of preference.

A candidate who wins over one-tenth of all first-place votes is immediately elected to the council, while candidates with the fewest number of first-place votes are eliminated from the race. The surplus votes of the winners, along with the votes of the eliminated candidates, are then transferred to the next candidates listed on the ballots. This process of redistributing votes continues until all nine seats are filled.

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