Former Alaska Governor Sarah Palin tells Fox News that none of the GOP presidential candidates have fully proven themselves as the GOP's best option in 2012. The remarks could be seen as an attempt to clarify earlier remarks that she didn't think Mitt Romney was conservative enough to win the Republican presidential nomination.

"I think the majority of us are not yet convinced that not just he, but that any of the candidates yet, are the one who will best be that contrast to Obama," said the former vice-presidential candidate on "Fox & Friends."

Palin also said it's subjective when measuring a person's conservatism.

The 2008 Republican Vice Presidential Nominee also listed a few questions she said were important for the candidates to answer: "Were they pro-abortion before and now perhaps they're pro-life? What allowed that switch, kind of that flip-flop? How have their positions evolved over the years? Were they pro-big government, pro-increase of taxes back then and where are they now?"

Romney has been accused of flip-flopping on abortion and tax issues by his rivals throughout the campaign cycle and Palin's remarks could be taken as another knock on the former Massachusetts governor.

In an appearance on "Fox & Friends" just before Palin's, Romney responded to Palin's original comments on "Fox News Sunday" where she questioned his conservatism. The former Massachusetts Gov maintained he wasn't quite sure why Palin didn't think he was conservative enough to be the nominee.

"I'm pro-life, pro traditional Marriage. I believe in the second amendment," Romney said. "As governor action I balanced the budget. Every year I was in office, put in place a $2 billion rainy day fund, cut taxes 19 times."

Romney also added that he's grown more conservative as he's gotten older, which Palin later called a "good sign."

Jason Donner is a Fox News Producer based in Washington, D.C. Follow him on Twitter: @jason_donner