Mr. DeStefano received about 90 percent of the delegates ' votes at the labor convention in New Haven , said John Olsen , the president of the Connecticut A.F.L.-C.I.O . Mr. Olsen said the federation voted for Mr. DeStefano over Mayor Dannel Malloy of Stamford based on Mr. DeStefano 's long history of helping unions in New Haven negotiate contracts with large institutions like Yale University .