The Northeast in general was a disaster for the Republicans in the 90s as well. Bush Sr. would have won NJ in tied PV in 1992, Clinton only won it by 2 points. In 1996 Clinton blew Dole out of the water by 18 points.
I only briefly mentioned it above but I think gun control (which was first a national issue in 1992) was the key issue driving this change. At a stroke it helped neutralise the weak on crime attacks that had killed Democratic candidates in the Northeast suburbs in the past while creating a new and popular wedge issue for Democrats there - by 1996 Clinton was very effectively campaigning on banning "cop-killer bullets" etc..
Of course the flipside was the Democratic collapse in rural areas post-Brady Bill, beginning with the 1994 midterms.