That may change.

The leader of the largest Democratic county organization in New York, Vito Lopez of Brooklyn, will be meeting within the next few weeks with Barack Obama to discuss a possible endorsement of his Presidential campaign, a Democrat with firsthand knowledge of the arrangement said.

Mr. Lopez, who presides over the party machine in a county with 884,000 registered Democrats, was among a handful of state legislators not on the Capitol steps when Hillary Clinton’s Presidential bid was endorsed by a series of Democratic state lawmakers, including Governor Eliot Spitzer and State Attorney General Andrew Cuomo.

If he went with Mr. Obama, Mr. Lopez would be the first prominent member of the Democratic firmament to endorse someone other than Mrs. Clinton.

A former social worker first elected to the Assembly in 1984, Mr. Lopez has been an extraordinarily undisciplined standard-bearer for his party over the years, demonstrating a predilection for attention-grabbing acts of rebellion. He has, at various times, supported Republicans for local office and backed primary challenges to incumbent Democrats.

When he became the county leader late in 2005, Mr. Lopez said that his organization was supporting “all of the Democratic candidates,” but declined—under direct questioning—to say the name of Freddy Ferrer, the Democrat who was then running for Mayor, according to a Village Voice article written at the time.

Meeting with Mr. Obama—and becoming the only county chair in New York to do so—would certainly have the effect, once again, of boosting Mr. Lopez’s profile.

Whether the meeting would be anything more than a publicity-generating exercise is another story. One source in Mrs. Clinton’s campaign said that Mr. Lopez assured them that he would be supporting her Presidential bid in the end.

Mr. Lopez wouldn’t comment for this story.

The lawmakers who have already openly declared their support for Mr. Obama’s candidacy are State Senator Bill Perkins of Harlem and City Councilwoman Helen Foster of the Bronx.

In addition, four lawmakers from Brooklyn—U.S. Representative Yvette Clarke, State Senator Eric Adams, Assemblyman Hakeem Jeffries and Assemblyman Karim Camara—as well as Assemblyman Keith Wright of Harlem, have conspicuously withheld support from Mrs. Clinton.

Mr. Jeffries said that his Brooklyn colleagues have agreed to revisit the issue next month, at which time they may all decide on a candidate or endorse separately.