Republican Senate candidate Christine O'Donnell's interview with Delaware radio host Dan Gaffney on Thursday offers a pretty good indication of why Rep. Mike Castle (R) is largely ignoring her primary challenge.

The exchange between O'Donnell and Gaffney is cringeworthy. The radio host, who endorsed O'Donnell's Senate bid against Joe Biden in 2006, began by confronting her about her statements that she had won two of the state's counties against Biden that year. 

After O'Donnell denied she ever made such a claim, Gaffney played audio of O'Donnell at a campaign rally proving she did. The two then argued over whether the candidate tied Biden in one county. Listen to the audio here.  

The two also sparred on whether O'Donnell has paid off her old campaign debts, an issue the state Republican Party and Castle supporters have raised repeatedly. 

"Isn't this what's wrong with Washington, D.C., that we borrow money, we collect money, and we don't pay off our old debts. If I can't expect my Senate candidate to pay off old debts…" Gaffney said.

"Dan are you kidding me?" interjected O'Donnell. "What happened? Is Castle paying you off?" 

The interview only got worse from there as Gaffney announced he had "serious questions" about O'Donnell's bid this time around, and at one point he actually turned O'Donnell's microphone off as the candidate continued to speak over his questions. 

Since Joe Miller's win in Alaska's Republican primary over Sen. Lisa Murkowski (R), O'Donnell has worked to paint her candidacy as the next potential Tea Party-backed upset bid. 

The Tea Party Express plans to run TV and radio ads on O'Donnell's behalf, but the state Republican Party is openly hostile to O'Donnell's bid and fully behind Castle. The primary is September 14. 

-Updated at 12:25 p.m.