Beau Biden, the son of Vice President Joe Biden, was long expected to run for his father's Delaware Senate seat in 2010. In November, polls even showed Biden surging ahead of expected Republican opponent Michael Castle. But this morning, Beau Biden sent an email to supporters announcing he will not run, instead seeking reelection as Delaware's Attorney General. It's just one race, but every seat in the Senate matters and, with a difficult 2010 election cycle ahead for Democrats, Biden's decision doesn't look good for the party.

• Dems Are Panicking  The Washington Independent's David Weigel declares Castle, "the most popular politician in the state," as "now prohibitively likely to take the seat over for Republicans." He calls Biden's drop-out "an indication that Democrats are panicking about bad polls and bad economic numbers and don’t want to stake their careers on the whims of 2010 midterm voters." Weigel tweeted, "Even if Dems end up beating Castle, this is a 'OMG we're doomed' message to reeling Democrats."

• If They Weren't, They Will Now  RealClearPolitics's Mike Memoli sighs, "You can just hear Democratic candidates and potential recruits saying, 'Well if the VP's son doesn't want to run...'" Memoli calls it bad news for the Democratic party "holding onto its increasingly precarious majorities in Congress."

• Bodes Poorly for Dems Nationwide  The Hill's Aaron Blake calls the move "a big blow to Democrats, as they had said for months that they expected him to run, even as he hesitated upon a return from a deployment in Iraq. It is the latest bad news for Democrats in a cycle with a growing number retirements and candidates bowing out. It's not clear where Democrats go from here."

• No Good Alternative Candidates  The Washington Post's Chris Cillizza thinks Biden has "doubts about a candidacy in the wake of the defeat of state Attorney General Martha Coakley in a Massachusetts special election, a race cast as a sign of just how bad the national environment had grown for Democrats." Cillizza surveys the field of potential Democratic candidates to take over, and though he finds some solidly popular possibilities, concedes, "No matter who Democrats nominate, however, Castle is a clear favorite."

• An Unknown Dem Could Win  Public Policy Polling's Tom Jensen suggests Democrats may be better off. "[I]t's not quite as end of the world for the party as you might think," he writes. "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."

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