New York, NY —

This weekend, Bronx Democrats will determine whether Assemblyman Jose Rivera can keep his post as chairman of the Bronx Democratic Party. In a rare insurgency, fellow Assembly members are trying to oust him. WNYC's Elaine Rivera reports.

For most people, the minutiae of local politics escapes them. Take the county party chairs of the five boroughs. The average voter could not name them let alone define what they do. But they have tremendous influence over political life in the city.

Veteran political consultant George Arzt explains.

ARZT: The county leader can provide money, manpower and strategy, organization to anybody running who the organization is backing. It's a very, very powerful post no matter even if you're from Staten Island it holds power.

REPORTER: The county chairman anoints candidates for judgeship, district leader, City Council and statewide legislative offices.

Political observers like Arzt say it's rare for a chairman to be challenged. But in the past few weeks, Assemblyman Jose Rivera - chairman of the Bronx Democratic Party for six years - has faced an unusual coup. A group of Assembly members who have called their movement the Rainbow Rebellion want to throw him out.

ARZT: Well, I think there's a civil war. There's the people who like Jose and the people who don't like Jose. Jose's leadership for some has been divisive for others not so....

REPORTER: The Rainbow Rebellion is so named for the multi-ethnic backgrounds of its members. It includes Bronx Assemblywoman Aurelia Greene. She says what sparked the rebellion was an obscure civil court judicial race in which the Bronx political establishment backed Elizabeth Taylor, who is African American.

The rebels say that Rivera told them he would support Taylor but then backed another candidate, Maria Matos, who is Latina. Greene says that was the last straw.

GREENE: We came together because we felt that there have been too many injustices. What happened with Elizabeth Taylor was what we have been seeing over the years what has happened to a number of people. This is nothing new. But this was the breaking point.

REPORTER: Greene was one of several Rainbow rebels who attended a rally Monday to call for Rivera's ouster.

Assemblyman Carl Heastie led the rally. He contends that Rivera turned against him and other black, Latino and white incumbents by supporting the candidacies of rival Latinos.

HEASTIE: The politics of division, the politics of pitting people against each other, the politics of not being honest with each other, the politics of not working together - people are tired of that and we want to change that direction.

REPORTER: Assemblyman Rivera declined to comment, but Michael Nieves, spokesman for the Bronx Democratic Party, vigorously defends the chairman. He says Rivera never made any promises to back anyone and he says the claims that Rivera partook in racially divisive politics are absurd.

NIEVES: This is a man who's participated in the civil rights struggle, this is a man who organized gypsy cabs, this is a man who visited the state of Israel five times, jumped over the fence in Bitburg. This is a guy who has a history with all the people of this borough. This guy is not divisive this guy is not anti-black or anti-Semitic. This guy is all inclusive.

REPORTER: Nieves says Rivera's opponents are actually angry because the Assemblyman made unpopular decisions in their districts.

This Sunday, hundreds of Democratic committee members - including the Rainbow rebels - will gather in the Bronx for their meeting held every two years. They'll vote to keep - or end - Rivera's controversial leadership. For WNYC, I'm Elaine Rivera