New York, NY —New York Assemblyman Ruben Diaz Junior is casting himself as a coalition builder, as he officially announces a run for the Bronx borough president's seat. WNYC's Elaine Rivera reports. REPORTER: Diaz appeared to be taking a page out of President Obama's handbook by pledging to unify a party and a borough that's been mired in factional infighting. On the steps of borough hall, Diaz was surrounded by a diverse group of elected officials who are throwing their support behind him. Besides being a conciliator, Diaz says he wants to reduce the borough's high unemployment rate and create more affordable housing. He also says he wants to bring attention to the disproportionately high rates of asthma and HIV cases in the Bronx. Missing from the event were Bronx Assemblyman Jose Rivera and his son, City Councilman Joel Rivera, who said last week he won't run for borough president. The elder Rivera is fighting with county leaders and has filed a legal appeal to get his seat back as Bronx Democratic County Chairman. He lost the seat last fall after key Bronx legislators withdrew their support for him. Diaz says he hopes to meet with the Riveras in the near future. For WNYC, I'm Elaine Rivera. REPORTER: So far, Diaz is the only candidate that has qualified for the April 21 special election, after getting more than 16,000 signatures, four times what's required.