That's a stretch. They base their story on exit polling. It's no surprise that those who left their homes to actually vote would skew favorably to Coons. There is absolutely no method of determining if Castle would have won in Christine's place.
Don't get me wrong; I wanted her to win, and prefer strong conservatives to run rather than the Castles of the world, but it's a bit silly to assume Castle would have lost. But I doubt a Castle win would have been satisfying at any rate. Better to have sent the message within the GOP that conservatives will be favored in the primaries.
I was answering the question of what the exit polls showed, and the answer isn’t a stretch, it’s a fact.
As for the the hypothetical of what would have happened in an actual race, I agree completely: that is unknowable. I wish somebody would explain that to Karl Rove and David Frum. The only thing we know right now - with the benefit of hindsight - is that O’Donnell couldn’t win a general election - and Castle couldn’t win a primary.
Maybe this is what long-term change looks like. After all, a conservative can never win the general without winning the primary. Or maybe this is just Delaware, and it’ll always be left-wing...