Outgoing Delaware Lt. Gov. John Carney says in a podcast (go to about 19:45):
It's been difficult to get people to step up to the plate and run against Congressman Castle. I gotta tell you, that's something I'm looking at right now.
This is pretty big news - Carney would probably be our best bet to take on Castle in 2010. (DE, regularly blue for several cycles, went for the Obama-Biden ticket by a 62-37 margin.) Carney also mentions that he might be interested in a Senate run. However, in this interview, he suggests that he's not interested in repeat his bruising 2008 gubernatorial primary experience in a Senate face-off with, say, Beau Biden. So if Beau runs for his dad's old seat, Carney could well take on Old Man Mike.