That is both logical and explainable--there are many people who live in Pa but work in New Castle County DE. As such, they vote in PA and not in DE. I live about 2 miles from Joe Biden's home and about five miles from the Pa State Line.
Probably getting money from Pa democrat party to vote in PA. #bidensforsaleHe should be voting where his primary residence is at. Could be he's never updated his voter registration.