Several Republican operatives in Iowa, where voters will have the first say on nominating the 2016 presidential candidates at the state caucuses in a year's time, were doubtful on Monday that Palin would enter the race.
Voters in the state are typically the first Americans to have their say on the country's presidential hopefuls, thanks to the Iowa caucuses.
11.55am: CNN reports that the Rick Santorum campaign has raised $2m in the two days since he "won" the Iowa caucuses.
So let's take a look back at some of the best: It's not exactly the White House, we know, and no, it wasn't the actual Iowa caucuses either.
Republican presidential candidate Rick Santorum is enjoying a bump in the polls in New Hampshire as a result of his success in the Iowa caucuses.
Iowa has caucuses but New Hampshire has a primary.
In the caucuses, people gather at neighbourhood centres, argue on behalf of their candidates and then go off to vote, a version of democracy that is fun to watch but slightly skewed.
Appearing at an all-day political beauty contest in front of voters whose caucuses will be the election's first nominating process next January, big-name Republicans from statehouses and congress explained why they had the vision and public appeal required for nationwide victory.
In a speech at the Brookings Institution that underlined both the vibrancy of his economic critique and his distance from the political mainstream, Sanders, a 73-year-old liberal firebrand who runs as an independent but caucuses with the Senate's Democrats, said he was giving "serious thought" to mounting a campaign – though he acknowledged it would be a long shot.
So that's $2m more than he had the day before the Iowa caucuses.
The Republicans and Democrats each hold their own set of caucuses.
