New Jersey, especially by the Hudson, is indeed very diverse. The areas that swung/trended Romney were the mountainous northwestern counties which are very white and quite wealthy (NY exurbs). However, the rest of Jersey is a very different beast from the Catskills (and Connecticut, which is even richer and much whiter than Jersey)
Sandy had to have been a factor in New Jersey, given that Obama also had swings in the Jersey Shore (which is traditionally trashy rich white people
), but Hudson County basically represents everything the GOP has collapsed with; Latinos (including now Cubans; my hometown of Union City is also known as "Havana on the Hudson" and votes overwhelmingly Democratic) and Asians, the group which the GOP could probably pick up (see what Harper did) but is doing a very good job at pissing off. Bob Menendez, who was the mayor of Union City, did a little worse than Obama with wealthy whites but even better with Latinos.
I'd be interested in seeing an exit poll of the 2009 gubernatorial race. Obviously Christie won a lot of white Obama voters, but he had to have done much better than Romney with Latinos, Asians, and blacks (NJ also has a fairly high black population which vote about how you would expect).
