President Trump narrowly won Pennsylvania in 2016. This year, the question is whether big turnout in the Democratic strongholds of Pittsburgh and Philadelphia can deliver his Democratic rival, Joe Biden, a win.
In particular, Philadelphia has been a focus for Trump; four years ago, only 15% of the city's voters picked him. Trump has claimed — with little evidence — that the local election system is corrupt. His critics say the president is trying to suppress turnout in the city.