Money is part of that. PA is a huge media market and without money he really couldn’t compete. So I take him at his word.
No point in risking the humiliation of a big defeat in your home state when you don’t have the money to do anything to mitigate that risk.
The Philthy media market alone is huge and expensive. Add having to do Pittsburgh and all the small markets in between, it is very expensive. The money spent in the Toomey/Sestak race were mind blowing for a US Senate race compared to other states.