Somewhat relevant (though not entirely the whole story by any means) that New Jersey in 1990 was 79% White, whereas by 2000 it was only 72.6% White and is now 68.6% White...
People really make a foolish assumption that these states were similar places to their current incarnations when analyzing how our political boundaries have changed. A red state becoming a blue state doesn't necessarily mean that the TYPES of voters who made it a red state have stopped voting Republican; it might mean that the makeup of the state's electorate has fundamentally changed.
Demographics of New Jersey per US Quickfacts 2015:
56.2% Non-Hispanic White
72.6% White Alone(Including White Hispanics I would guess)
19.7% Hispanic or Latino'
14.8% Black or African-American
9.7% Asian
2.1% Two or more races
