PITTSBURGH — National politicians have used this city in the past two decades as either a visual prop or an alliteration. They come here, to a city many people associate with the working class, either to make a political point or to give themselves some much-needed working-class street cred.

Former Democratic presidential nominee John Kerry, Massachusetts’s multimillionaire senator, used the city as a backdrop for announcing his pick for vice president, then North Carolina Sen. John Edwards, another millionaire.