At least two GOP senators who donated to Rep. Mike Castle's (R-Del.) failed primary bid against Tea Party candidate Christine O'Donnell said Wednesday morning they were unsure whether they would contribute to O'Donnell's long-shot general election bid.

Centrist Sen. Susan Collins of Maine and conservative Sen. Thad Cochran of Mississippi both said they were surprised by O'Donnell's six-point margin of victory over Castle. O'Donnell faces Democrat Chris Coons in the November election, and polls show the prospect has dimmed Republican hopes of retaking control of the Senate.

Collins and Cochran each contributed $10,000 to Castle's campaign.

"I don't know her at all," Collins said of O'Donnell. "I was a strong supporter of Mike Castle, and I'm disappointed he did not prevail. This came as such a surprise to me. I really don't know her yet, so it's premature for me to make that decision. ... Certainly had Mike Castle won, I was very optimistic that we would pick up the Delaware seat. I am no expert on Delaware politics, but friends of mine tell me that prospect is now much more difficult."