The Broadway Democrats, a party club on the Upper West Side of Manhattan, voted last night by a wide margin to endorse insurgent gubernatorial candidate Cynthia Nixon against her primary target, incumbent Gov. Andrew Cuomo.

The club members also backed Brooklyn Councilman Jumaane Williams over incumbent LG Kathy Hochul, and former NYC Councilman Robert Jackson, who is challenging Sen. Marisol Alcantara, a member of the now-debunked IDC, in the September primary.

According to a source who took part in the voting, the final outcome was not close.

Nixon received 23 votes to Cuomo’s nine, while six people opted for “no endorsement.” In the LG race, Williams got 25 votes to Hochul’s 12, while 2 people would have preferred to see the club remain neutral in the primary.

The existence of party “clubs” might sound a little alien to people who live upstate, where they are not the norm – though some do exist, mostly in urban centers like Albany and Buffalo. But they are prevalent in New York City, providing an entry point for grassroots politics and also serving as a key organizing force.

Club endorsements are important because members act as volunteer foot soldiers in campaigns, circulating petitions on behalf of chosen candidates and assisting with literature drops, phone banks, and other GOTV efforts.

As a result of this vote, the names of Nixon and Williams will be on the petitions circulated by the Broadway Democrats when petitioning begins next month. According to my source, it could also potentially assist Nixon is hitting the all important 25 percent mark to get on the ballot in the weighed state committee vote at the state convention.

The convention votes are weighted and the 69th Assembly District, which is where the Broadway Democrats are located, is the most Democrat-dominated in the state, and also generally has the highest turnout, which means its support matters when the weighted vote is calculated.

This is not the first club to back Nixon over Cuomo. A source says that the Three Parks Independent Democrats, which is in the 67th Assembly District, also voted this week to support the governor’s primary rival.

The Central Brooklyn Independent Democrats threw its support to Nixon last month.

Meanwhile, Cuomo has been endorsed by The Martin Luther King Jr. Democratic Club, the Benjamin Franklin Reform Democratic Club and the Hell’s Kitchen Democrats.

As mentioned earlier, these clubs, while small, can be a potent force when it comes to working on a candidate’s behalf. Also, people who join these organizations tend to be true believers – the sort who turn out to vote on primary day – and the more of them that are backing Nixon over Cuomo, the more concerned the governor might be.

Then again, the Upper West Side is know as a bastion of liberalism, so I guess it’s not really a surprise that some of these clubs are going to for the left-of-center option, following the lead of the Working Families Party, Citizen Action and others. We’re also talking about a neighborhood that knows Nixon well, as she used to call it home.

I believe Nixon and her wife have since decamped downtown.