Why is Mitt Romney writing off Iowa when he's doing so well in the polls there?

Being a geographical "favorite son" in NH, he has got to deliver a crushing victory by at least 20-25 points to set a foundation to stay in the game. I gather the internal polling in Iowa shows he would have to dump even more cash than he did in 2008 to bolster his chances in the quirky caucus system and - campaign-wise - it's just not worth the expense. Cash, staff and realistic chances will split the real contenders from the pretenders by the first "Super Tuesday."