The former Republican vice-presidential candidate, Sarah Palin, has endorsed Newt Gingrich as the party's presidential candidate to become the highest-profile politician to oppose a Mitt Romney nomination.
Palin, who rose to the forefront of American politics in 2008 when she was selected as John McCain's running mate, had been coy about who she would endorse for 2012.
But speaking on the Sean Hannity show Palin admitted that if she were in South Carolina, scene of the next Republican primaries, she would "vote for Newt".
She added, however, that she was keen to see the primary contest run as far as possible, viewing a tight race as good for keeping the candidates on their toes. She said: "Iron sharpens iron, steel sharpens steel."
"If I had to vote in South Carolina, in order to keep this thing going I'd vote for Newt and I would want this to continue," Palin said.
"More debates, more vetting of candidates, because we know the mistake made in our country four years ago was having a candidate that was not vetted to the degree that he should have been so that we knew what his associations and his pals represented and what went into his thinking, the shaping of who our president today is."
Her husband, Todd Palin, has already backed Gingrich for president.