Pennsylvania presidential polls: Who's leading —Donald Trump or Hillary Clinton?

The day after the second presidential debate in St. Louis, Donald Trump headed to Pennsylvania, a key battleground state that he's hoping holds the keys to the White House.

Who's leading the Pennsylvania polls?

But most polls show Hillary Clinton with a clear advantage in the Keystone State. The RealClearPolitics polling average finds the former secretary of state leading the Manhattan businessman 48% to 39% in a head-to-head face-off.

Why is Pennsylvania so important?

The state has 20 coveted electoral votes. Back in May, FiveThirtyEight's David Wasserman declared Pennsylvania "a tipping point" for the outcome of the election. 

"Western Pennsylvania is driving the state's rightward drift — its voting patterns now resemble greater Appalachia's more than those of the Philadelphia suburbs," he wrote.  

And FiveThirtyEight predicts that there is an 87% chance that Clinton will win Pennsylvania.