Thanking supporters, Mr. Booker returned to many of the lines he used to open his campaign in June, promising to bring a new kind of politics to Washington.

“Too many people are forgetting that the lines that divide us are nothing compared to the ties that bind us,” he said. “It forgets that old saying, ‘If you want to go fast, go alone; if you want to go far, go together.’ ”

Conceding the race before a crowd of a few hundred supporters at a banquet hall in Bridgewater, N.J., Mr. Lonegan called the race a victory, even in defeat, and thanked the prominent conservatives who had come to the state to campaign for him, including Rand Paul and Sarah Palin.

“We came well closer to winning this election than anyone ever expected,” Mr. Lonegan said to loud cheers. “The big Washington power groups and consultants said we couldn’t win. Well, maybe if they had played a role in this election, we would have won.”

Mr. Booker grew up in the wealthy North Jersey suburb of Harrington Park, where his parents, some of the first black executives at I.B.M., helped integrate the town.

A graduate of Stanford and Yale Law School, and a former Rhodes scholar, he was a celebrity even before he became mayor — with an Oscar-nominated documentary about his first, failed race in 2002. He was elected in 2006 to replace Sharpe James, the longtime mayor who later served time in prison for fraud.

Mr. Booker brought excitement to a city that has long struggled to shake off the cloud of the riots that nearly destroyed it 46 years ago. And with his national profile, he also attracted more business development, including Newark’s first new hotel and supermarket in decades, and millions of dollars in philanthropy, including a $100 million pledge to the city’s long-failing schools from the Facebook co-founder Mark Zuckerberg.