ReutersModerate Republican seeks Biden's old US Senate seatReutersWASHINGTON, Dec 23 (Reuters) - Michael Castle is a member of an endangered species in the US Congress: He's a moderate Republican. He's also a key figure in next year's election. Castle is running to fill the Senate seat for Delaware ...Joe Biden's Senate Seat Attracts GOP's Michael CastleMyStateline.comJohn CornynTPMDC (blog)Sen.