Duane, the state senator from Chelsea, didn't attend the event, but has officially come out in support of Thompson, a fellow Democrat.

Duane was among the notable absences from another endorsement event recently on the Upper West Side, which featured Representative Jerry Nadler, State Senator Eric Schneiderman, Assembly member Linda Rosenthall and City Councilwoman Gale Brewer.

Through a spokesman, Duane, said, "From LGBT issues to his oversight of New York's Mitchell-Lama housing program, Bill Thompson has been a consistently effective and progressive advocate for the people of this city. He represents strong Democratic values and I wholeheartedly endorse him for Mayor."

Now, the only Democrats on the West Side who have not endorsed Thompson are City Council Speaker Christine Quinn and Borough President Scott Stringer.

Both employ a consultant, Josh Isay, who also advises Bloomberg.