Veteran Republican strategist Karl Rove fired back at GOP Senate candidate Christine O'Donnell (Del.) Wednesday in a war of words that began when the former Bush adviser publicly doubted the ability of the Tea Party favorite to capture Vice President Joe Biden's old Senate seat in November.

Rove said on Fox News's "Hannity" program last night that O'Donnell hadn't answered a series of troubling questions about her past. "I'm for the Republican, but I got to tell you, we were looking at eight to nine seats in the Senate," Rove said. "We are now looking at seven to eight in my opinion. This is not a race we're going to be able to win."

"I think he's seeing that he's one of the so-called experts whose credibility was hurt last night," O'Donnell said on "Fox and Friends."

“Everything that he is saying is un-factual. And it’s a shame because he is the same so-called political guru that predicted I wasn’t going to win. And we won and we won big,” O’Donnell told ABC. “So I think, again, he is eating some humble pie and he is just trying to restore his reputation.”

Rove brushed off O'Donnell's statements on Fox later, but stressed that he believes the Senate hopeful is in trouble.

"She belives she's going to win," Rove said, but said O'Donnell needs to explain tax problems in her past and controversy surrounding her claims of a college degree when she hadn't yet received it, as well as lawsuits over her college bills.

"These and other troubling personal background, she thinks she has explained them," Rove said. "If she wins, more power to her."

Rove said "she's right on the issues," but Delaware voters are going to want to know more than that. "She's got to answer these troubling questions."

He acknowledged that O'Donnell's victory over Rep. Mike Castle was a "huge upset."

"She's got a tough road ahead," Rove added. "She can't simply say, 'Oh go to my website, I've got the answers there.' "