In an interview with The Hill, O'Donnell said the same sort of outside support that helped promote Miller in Alaska could put her over the top in her primary against Castle.
"We're already ahead of where Joe was in the polls," O'Donnell said. "If we could just get that extra push."
Of the Tea Party Express and other third-party groups like the Club for Growth, O'Donnell said, "I hope they see the potential difference they could make."
O'Donnell is working hard to gin up enthusiasm for her challenge to Castle, one of the most centrist Republicans in Congress. She noted that her consulting team includes strategists who worked on Doug Hoffman's race in the special election for a New York congressional seat last year.
She's also trumpeting polling from earlier in the year showing her ahead of Democrat Chris Coons. More recent polls on that hypothetical general-election match-up, however, put Coons ahead. A Rasmussen poll from earlier this month shows Coons ahead by double digits.
The Republican establishment in the state is also downright hostile to O'Donnell and doesn't seem to fear any sort of backlash from conservative activists or voters.
State Republican Chairman Tom Ross labeled O'Donnell "a perennial candidate who lacks the standing in Delaware to get elected to anything."
Ross also took a shot at the Tea Party Express, calling it "unfortunate that a group like that would get involved and try to override the choice of local activists in Delaware."
Ross said that O'Donnell was defeated soundly at the state's GOP convention and accused the Tea Party Express of "monkeying with the primary process."