Partisan Democrats are delighted about Christine O'Donnell's Republican primary victory over Rep. Mike Castle in the race for the open Delaware Senate seat. I’m despondent. From the Democratic point of view, the defeat of the moderate, well-known Castle turns what had looked to be a lost cause into a likely win. Keeping the seat in Democratic hands could be the margin of control in the Senate. So the folks who focus on electing Democrats and keeping a Democratic majority can't be blamed for breaking out the champagne over O'Donnell's win. Not me, for two reasons. First, I had thought the...