Toomey's campaign was almost single-handedly sunk by Christine O'Donnell. He was up with a comfortable lead, but then O'Donnell and all her mishigas started to bleed over from DE, due in no small part to the fact that almost of of DE shares a media market with eastern PA.
I think without O'Donnell, Toomey wins that race by at least 6.
I am not an expert :-)! Moreover, a lot of this is anecdotal ... however :
I live in Western PA and saw a LOT of disdain for Dan Onarato here. If I am not mistaken, a majority of voters here in Allegheny County went for Corbett. Onarato was *well* hated. Obama is a million times worse than Dan, but I know W. Pa will flip back to “safe Obama” in 2012. I think the whole Governor race may have offset what you saw with O’Donnell (I do agree with your point by the way though I didn’t want to see Castle in there either).
For the record, I liked O’Donnell and LOVE Sarah Palin ... I just think we need someone else running in 2012. I think DeMint would be the right answer. The election is still two years out ... a lot will happen between now and then!