Beau Biden, son of Vice President Joe Biden, won’t run for United States Senate in Delaware. That leaves Rep. Mike Castle (R-DE), who declared his candidacy back in October, without a Democratic opponent. Republicans are now likely to pick up Vice President Biden’s old seat.

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So let’s see. Republicans have already picked up a Senate seat in Massachusetts. What other seats are they likely to take? Indiana, Delaware, Nevada, Arkansas, and Colorado. They also have a good chance in Pennsylvania, California, and Illinois.

That would be a pick-up of 9 seats during 2010. The chamber would be split.