A new Public Policy Polling survey shows there's a real possibility of a major upset in the Delaware U.S. Senate primary on Tuesday.
Christine O'Donnell (R) leads Rep. Mike Castle (R), 47% to 44%.
Key finding: Castle has an overwhelming 69% to 21% lead with moderate voters but they only make up 33% of the likely primary electorate. O'Donnell has a 62% to 31% lead with conservatives that's more than enough to propel her to the overall lead.