Republicans circulated audio of a testy, 22-minute interview that O’Donnell had with radio station WGMD on Thursday. Party officials also have said she inflated her resume and made flat-out untrue statements while being dogged by questions about tax liens and foreclosures. Castle says she has misrepresented his record.

“She’s not a viable candidate for any office in the state of Delaware,” state party chairman Tom Ross, who is backing Castle, said in a telephone interview. “She could not be elected dog catcher.”

Republicans said Castle’s campaign is preparing negative television ads against O’Donnell. The commercials would air in the week leading up to the primary. The campaign also has created a website, RealChristine.com, a clearinghouse of negative O’Donnell stories.

“Unfortunately, the truth always seems to be an issue,” said Ross. “Her version of reality doesn’t jibe with any of the facts.”