McConnell is a very good, crafy politician; he's not smart on policy or anything like that, but he's a political creature, hence Politico pointing out it's odd that he would miscalculate a vote like that.
Anyway, I don't think Gingrich will be finished if Romney wins Iowa and NH. He should still win SC, and Florida will be competitive if Gingrich doesn't implode his own campaign.
Santorum has put in more work on the ground in Iowa than anyone but it hasn't resulted in much of anything. If it wasn't for the holidays coming up I'd agree he could maybe make a run, but it's probably too late. And if he doesn't win Iowa, it's over for him. I expect Gingrich, Paul, and Romney to finish ahead of him.
In terms of endorsements...they're one of the most effective things in US politics. Romney had yet to get any meaningful, nation scale endorsements outside of Chris Cristie's, and I don't think that is nearly as important as Palin's endorsement.