In the same month, sitting Hamilton mayor Bob Wade announced he would not seek re-election in the 2003 municipal election. On April 28, 2003, Di Ianni announced he would seek the office of mayor indicating that he believed Hamilton to be at a crossroads with regard to development. Di Ianni's main opponent in the race was former provincial NDP cabinet minister David Christopherson and the race focused considerably on the construction of the Red Hill Expressway, of which Di Ianni was in favour and Christopherson was opposed. The candidates sparred frequently on the campaign trail, with Di Ianni promoting his municipal experience and support from the business community while Christopherson highlighted his time in cabinet and support from organized labour and progressive political organizations. On election night, Di Ianni defeated Christopherson by a margin of 52% to 39%. Speaking to reporters, Di Ianni noted he was immensely happy that the voters of Hamilton elected their first Italian-Canadian mayor by such a large margin.