Luke Ravenstahl, 28, became Pittsburgh's city council president in 2003 and the city's youngest mayor in 2006 when former Mayor Bob O'Connor died of brain cancer.
At campaign events with Ravenstahl, the New York senator praises the mayor for helping "re-energize Pittsburgh" as it struggles to find a new employment base amid the declining steel industry.
Ravenstahl and Clinton support boosting Pittsburgh's reputation as a manufacturing center by investing in clean energy technology.
Clinton, whose lead in the polls over her Democratic rival, Sen. Barack Obama, D-Ill., has slipped as they head toward Pennsylvania's April 22 primary, said she hopes Ravenstahl's age will discredit notions she lacks support from young Pennsylvania voters, The Washington Post said Wednesday.
Ravenstahl's role could help or hurt, the Post says, as he has both a bad boy reputation and, says his staff, a bit of a rock star status.
"The city loves him, because he's so fresh and so young," city Councilman Jim Motznik said. But his critics say he's "so young" he's made some mistakes, including using a city vehicle to take his friends to a Toby Keith concert.