In a large auditorium at St. Francis College in Brooklyn several days after the primary last month, the usual crowd of Democratic politicians shook hands and patted backs.
The meeting of the Brooklyn Democratic Party, a ritual that takes place every other year, was closely choreographed by the county party leader, Assemblyman Vito J. Lopez, who is a throwback to an era when being a political boss meant that nobody questioned your authority.
But this year, some uninvited guests crashed his party.
About 50 protesters, most of them in their 20s and 30s, stood outside waving signs (''Brooklyn deserves better!'' said one) and chanting slogans including ''No justice, no peace!'' until they were allowed into the auditorium, although a handful of burly men blocked their access to a smaller meeting of party leaders.
The protesters were from the New Kings Democrats, a progressive organization looking to shake up the Democratic establishment in Kings County. One of the leaders of the protest and the group is a boyish-looking 26-year-old named Lincoln Restler.
Mr. Restler is unknown to most New Yorkers, but he is making a name for himself in the local political world after pulling off an upset in last month's primary by defeating Mr. Lopez's preferred candidate for a seat on the Democratic State Committee.
Though it is an obscure office — mostly relegated to endorsing candidates and selecting the county party's leader — Mr. Restler's path to victory raised eyebrows among those who know that Mr. Lopez's role as a kingmaker in local races is almost never challenged.
Mr. Restler took on Warren Cohn, whose father, Steve Cohn, held the seat for nearly three decades and was stepping aside, seemingly bequeathing the seat to his son.
Despite the younger Mr. Cohn's strong support from the party, Mr. Restler pulled out a narrow victory, defeating him by 120 votes.
''It was truly like David and Goliath,'' said City Councilwoman Letitia James, who represents parts of Brooklyn. ''Some people, when you mention the name Vito Lopez they quiver. They're fearful. And here this kid comes and knocks him on his butt.''
The kid, Mr. Restler, has horn-rimmed glasses and a mop of curly brown hair and looks as if he could play Harry Potter. But he is serious about government and community activism. He works as a program officer for the city's Office of Financial Empowerment, is the secretary for Community Board 2 in Brooklyn and serves on the boards of the Pratt Area Community Council, a housing advocacy group, and the Fort Greene Association, a community group.
''I don't date much,'' Mr. Restler joked in a recent interview.
Like many fellow members of the New Kings Democrats, Mr. Restler polished his campaign skills on President Obama's White House bid. He traveled from Florida to Pennsylvania and South Carolina as a volunteer, knocking on doors, registering voters and working phone banks. And like the man he helped get into the Oval Office, Mr. Restler employs a familiar language of hope and change.
To earn his own victory lap, Mr. Restler said, he personally knocked on some 4,000 doors, shook hands outside subway stations every morning and put his family to work canvassing for votes on his behalf.
''It's hard to say no to somebody's mom,'' he said.
Mr. Restler positioned himself as an alternative to what he has called the ''embarrassing'' corruption of the Brooklyn Democratic Party — his Web site points out that three of the last four party bosses have been indicted — and to the concentration of power at the top in the hands of Mr. Lopez, who, along with nonprofit groups he controls, is being investigated by the city and the federal government.
''We weren't supposed to win this race,'' Mr. Restler said with a smile. ''The support that my opponent had before the race began was almost enough to win. And we needed to run a flawless campaign to pull this thing off.''
What Mr. Lopez and Mr. Cohn think of this new upstart is unclear. Neither man responded to phone calls and e-mails.
Beyond effective grass-roots campaigning and the anti-establishment mood of many voters, some political operatives attributed Mr. Restler's victory to the many new faces in his Assembly district, the 50th, which includes parts of Williamsburg, Greenpoint and Fort Greene.
''Younger urban professionals are moving here,'' said Lewis A. Fidler, another Council member from Brooklyn. ''These are neighborhoods that used to be characterized as conservative Hasidim, Italian and Polish communities. Clearly, that has changed.''
Mr. Restler's victory, he added, ''reflects that.''
Mr. Restler also enjoyed another advantage: money.
His campaign raised over $60,000, an enormous amount for a state committee race, about four times as much as Mr. Cohn raised.
Just over $35,000 in Mr. Restler's campaign fund came from about three dozen donations of $500 or more, including about $11,500 from his father, Peter Restler, who works in private equity. But Mr. Restler's campaign was quick to point out that 71 percent of all donations were made in amounts of $100 or less.
For Mr. Restler, accomplishing much with a position that pays no salary and has little power will probably prove a tougher task than winning.
''This is a symbolic victory,'' said Norman Adler, a political consultant who has worked mostly for Democrats. ''His challenge now is to turn a symbolic office into some sort of power center.''
Mr. Restler says he understands the challenge but described his new job as a bullhorn to use for community organizing — another echo of Mr. Obama. He said that he planned to be an advocate for local needs, like affordable housing in Williamsburg and more supermarkets in Fort Greene.
As he sat cross-legged on the grass in Fort Greene Park recently talking about plans for his district, he noticed a voice mail message pop up on the screen of his iPhone. It was a message of congratulations from Assemblyman Joseph R. Lentol, a Democrat who had supported Mr. Cohn in the election and who shares the district with Mr. Restler.
''I look forward,'' Mr. Lentol said, ''to working together.''
