What's the matter with New Jersey?

In an earlier post, I pointed out that that the identity of "red" and "blue" states today is completely different from what it was in the 1930s.  In fact, there have been significant changes since the 1980s.  For example, New Jersey is now often called a "blue" or even a "deep blue" state.  The figure shows the Democratic share of the vote relative to the whole nation in Presidential elections from 1916-2012.

From 1916 to 1992, New Jersey leaned Republican.  For example, in 1992 the national vote went for Bill Clinton over George HW Bush by 43%-37%, with 19% to Ross Perot.  In New Jersey, it was 43% for Clinton, 41% for Bush and 15% Perot.  But starting in 1996, the Democratic share of the vote has been 5 to 7 points higher in New Jersey than in the nation as a whole.  The timing of the Democratic shift in New Jersey was about the same as the Republican shift in West Virginia, although it hasn't been as large.