Christine O'Donnell, the former Republican Senate candidate and a tea party favorite during the 2010 election, has officially endorsed Mitt Romney for president.

O'Donnell made her endorsement during an appearance this evening on Fox News' "Hannity."

"It was not an easy decision because I too think any of our candidates would make a great president and a great candidate going against Barack Obama," O'Donnell said. "But I think there are certain tie breakers and I know that in making my decision I might be hurting some people but I think infrastructure and executive experience are important, and for that reason I'm endorsing Mitt Romney."

"I'm very happy," she added. "This is not anti-[Newt] Gingrich or anyone else, it's a pro Gov. Romney endorsement.

"I'm not arrogant to think that my endorsement will make or break his candidacy," she said, adding she hopes people just "take a second look" at Romney.

O'Donnell made clear that the Romney campaign did not "come to her," and that she went to the campaign. She said she would be willing to go out and campaign for Romney.

In a written statement, Romney welcomed the endorsement.

"Christine has been a leader in the conservative movement for many years," Romney said. "Christine recognizes that excessive government threatens us now and threatens future generations, and I am pleased to have her on my team."

In an exclusive interview with ABC News in October, O'Donnell said she was "70 percent" behind Romney, and confirmed that she had given money to his campaign. But at the time O'Donnell said she had also contributed to Herman Cain's campaign, and had plans to give to Gingrich and Rick Santorum.

O'Donnell, who struggled with her own fair share of bad press during her Senate campaign, told ABC News that she tends to "empathize" when she sees "Romney's record being so obviously distorted and twisted."

"I hope the fact that I stood up to the liberal establishment within my own party gives me the bona fides among conservatives to say this," she said. "I find the tone and nastiness of some of the things circulating around the Internet about Romney extremely offensive.

"It's politics of personal destruction aimed at our own and it's got to stop," she added. "Right now a lawn gnome could beat Obama in 2012, so, yes, we can be picky, but not nasty or malicious. If we don't stop the Republican cannibalism, we're simply turning this election over to the Democrats, who certainly don't deserve it."

O'Donnell won the Delaware GOP primary in 2010 by more than 53 percent of the vote against U.S. Rep. Mike Castle, but later lost to Democrat Chris Coons in the general election.