It's bad news for Democrats that Beau Biden's not going to run in Delaware. I'm not going to dispute that. But it's not quite as end of the world for the party as you might think:
1) Beau Biden is not an overwhelmingly popular politician in Delaware. When we polled the race there last month his favorability breakdown was 43/35. That's solid but it's not great. He trailed Castle by 6-8 points each time we looked at it.
2) Right now voters are very much down on the political establishment. A Castle vs. Biden race would have been establishment vs. establishment. Democrats have an opportunity now to field a candidate who can run more credibly as an outsider against nine term Congressmen Castle than Biden could have.
3) Yes, Democrats will likely have to run someone now with less initial name recognition. But remember that Scott Brown's name recognition was just about zero at this time two months ago. And Kay Hagan and Jeff Merkley were both pretty obscure before being elected to the Senate two years ago. Initial name id tends to be pretty overrated in statewide elections.
It would have been better if Biden had run but I don't think chances of a Democratic hold are that much worse than they were before.