Colorful Mayor of Providence Finds Comedy in Indictment
Mayor Vincent A Cianci Jr of Providence, RI, charged with running city government as criminal enterprise, ridicules federal investigation that resulted in his indictment; indictment charges Cianci and several other city officials with racketeering, conspiracy, extortion and mail fraud; Cianci is also charged with witness tampering; Cianci, who has been mayor for last 26 years--except for six-year break following assault conviction--responds by appearing on radio show to do comedic riff on case, and to portray federal law enforcement officials as bunglers of ill intent; in fact, one prosecutor admits inviting friends to view surveillance tape on Cianci, and businessman who first alerted federal agents to corruption in City Hall has been jailed for repeated domestic violence; Cianci, political independent, operates with total control; there is no Republican Party to speak of and many city Democrats hold their tongues to keep their City Hall jobs; photo (M)