Delaware Republicans call Senate hopeful Christine O'Donnell a liar who "could not be elected dog catcher."
The fierce attack underscores GOP fears of the tea party-backed candidate knocking off top recruit Rep. Mike Castle and winning the nomination.
The state holds its primary Sept. 14 and the GOP sees Castle as the best candidate for the seat long held by Vice President Joe Biden. Castle has been the state's lone congressman since 1993.
State Party Chairman Tom Ross said in an interview that O'Donnell is not a viable candidate for any office in Delaware.
The Tea Party Express has announced a six-figure commitment to back O'Donnell.