The New Republic's Noam Scheiber has (some of) Mitt Romney's internal polling from the last weekend of the campaign, and has discussed it with Romney pollster Neil Newhouse.
It's worth a few comments.
First, as Andrew Rudalevige notes, these polls do not justify the type of confidence that Team Romney was reported to have on election day. Romney is close, and closer than the polling averages had it -- but he's still losing. This set of numbers really doesn't inspire a lot more hope than the public polling did; both leave open a real possibility that Romney could win if it turns out he runs a bit better than the polls, but neither really give any reason to expect that.
Second: it's very hard to see any harm in it. Every campaign needs to act as though it believes it will win. But that means that every person in every campaign needs to act that way, and the easiest way to do so is to really believe it. I see nothing in this story, and generally I've seen nothing in any of the post-election coverage, to indicate that Romney's campaign erred in any way based on their apparent wishful thinking about the polls.
Third, in particular it's very hard to argue that redeploying resources to Pennsylvania at the last minute was a mistake. It's probably easier to argue that they should have been targeting Pennsylvania all along, but then again I'm not really aware of evidence that they made any significant targeting mistakes, either.
Fourth, it's very much worth tracking the consistency between what is now reported as the inside Romney campaign view and what (many, most) GOP-aligned news outlets were saying.
Fifth, none of this really gets to the key questions going forward, which as I see it are about (1) why Barack Obama's national vote wound up pretty high in the plausible range of what the fundamentals predicted, and (2) whether the Democrats have opened up a long-term electoral college advantage.
Now, I think all of this is based on the premise that there really wasn't much that Romney could have done about most of the lay of the land. Could he have discouraged African American and young voters from coming to the polls? Hard to see that. Could he have flipped the Latino vote? No, not really; on both policy and, really, rhetoric, his hands were tied by his party.
What he had the ability to do, especially in the final weeks of the campaign, was to move around resources to where they would be most useful. As far as I can tell, Team Romney mostly did a reasonable job of that. They also had control of their own turnout operation, which received lousy reviews...but it's pretty hard, I think, to tie that to polling-based overconfidence, or really anything beyond managerial incompetence (assuming that is that it's true, which we don't really know). So while there's plenty of interesting material in this scoop, I'm not sure how much it really tells us at the end of the day.