Mayor Luke Ravenstahl of Pittsburgh, debated his Democratic challengers, Carmen Robinson, a former police sergeant, and City Councilman Patrick Dowd. The D party primary, Tuesday, May 19, 2009. PITTSBURGH — When Luke Ravenstahl became the youngest mayor of a major American city in 2006 after his predecessor’s death in office, serious potential rivals sat on the sideline, biding their time. It has not happened. Even so, the primary race has been spirited, with City Councilman Patrick Dowd, 41, and Carmen Robinson, 40, a political newcomer and local lawyer, stirring the debate.