The defeat suffered by the Bronx County Democratic organization, which lost every race in which it supported a candidate in Tuesday’s primary, may mean new leadership for the county party.

The organization was opposed by a so-called rainbow coalition of legislators, which includes prominent black, white, and Hispanic lawmakers from throughout the borough. That coalition is expected by political observers and activists to move quickly to depose the current Democratic leader, Assemblyman Jose Rivera, as soon as Monday night.

Mr. Rivera’s choice for a countywide vacancy as judge of the civil court, Maria Matos, a law clerk, was soundly defeated by Elizabeth Taylor, who was backed by the insurgent coalition.

Ms. Taylor won 19,228 votes against only 10,406 votes for Ms. Matos. Mr. Rivera’s choice of Ms. Matos upset some African-American party leaders who felt that they have been systematically underrepresented on the court. Ms. Matos is of Puerto Rican background while Ms. Taylor is African American.

Mr. Rivera, who has held his post as Bronx Democratic party chief since 2002, has been criticized by some politicians for not being evenhanded in his treatment of the various Bronx contingents. Some also resent his family’s high profile. Mr. Rivera’s son, Joel Rivera, is a City Council member. His daughter, Naomi Rivera, was elected to the New York State Assembly in 2004 in a district adjoining his.

The choice of Ms. Matos provided an opening for Assemblyman Ruben Diaz Jr. of Soundview, who is interested in seeking to become president of the Bronx next year. He was expected to be opposed for that post by Council Member Joel Rivera, and thus there has been no love lost between Mr. Diaz and the senior Mr. Rivera.

Mr. Diaz joined with his Assembly colleagues, Carl Heastie and Michael Benjamin, both African Americans, and then with Assemblyman Jeffrey Dinowitz of Riverdale and his powerful Benjamin Franklin Reform Democratic Club to promote the candidacy of Ms. Taylor.

An enraged Mr. Rivera countered by putting up opposing candidates to Messrs. Diaz, Heastie, and Benjamin. But when the votes were counted Tuesday night, Mr. Diaz garnered nearly 86% of the vote against his opponent, Israel Cruz, Mr. Heastie drew 78% of the vote against Sherman Browne, and Mr. Benjamin got 62% of the vote against Sigfredo Gonzalez.

Yet another organization stalwart, 20-year veteran state Senator Efrain Gonzalez Jr., was soundly defeated by a former senator and City Council member, Pedro Espada Jr., by a 60%-40% margin, a final embarrassment for Mr. Rivera. Mr. Gonzalez is under indictment for allegedly diverting $400,000 in public funds through nonprofit front organizations for his personal use. He is scheduled to go on trial next May.

Emboldened by their clean sweep, the “rainbow coalition” is organizing to replace Mr. Rivera when the party convenes its biannual organizational meeting Monday night.

“The Bronx right now under the current leadership is laughable,” Mr. Diaz charged. “They’re laughing at us from the outside. We’re looking to repair that.”

Since Mr. Diaz is hoping to run for borough president, it is Messrs. Dinowitz and Heastie who are most frequently mentioned as possible replacements for Mr. Rivera.

But regardless of the outcome of Monday’s vote, the clout of the once powerful Bronx Democratic Party has been greatly diminished. “It has been exposed as a paper tiger,” Mr. Dinowitz noted. “And that is not a good thing for the people of the Bronx.”

Mr. Rivera was not available for comment.

awolf@nysun.com