Never thought she would last all the way through the primaries season, but it's nice to see her out already in Iowa. If Palin (her political role model, isn't she?) had been a candidate she might have scored big in Iowa, Texas and some other places but she wouldn't have had much of a chance to get the nomination - she is just too extreme to be a viable, winning candidate in the end, and both the top level of the GOP and many voters know that.
Santorum looks like he's got a better chance and undeniably he's an energetic speaker; Gingrich won't last all the way I think. Mitt Romney will be in all through till summer and likely beyond, unless he really trips on something. Ron Paul has a big and enthusiastic fanbase and he's not a spent force (which I think Gingrich comes across as, he's near seventy and really too much Reagan/Clinton era, and seems to have some, erm, "baggage"). So the top trio from Iowa would be the ones posted to fight it out.