Gun control and environmentalism. It's the same reason why Gore lost TN, AR, MO and WV. In the 90s gun control and environmentalism became hot button issues and the Mid Atlantic backed both. The NYC/NJ/CT suburbs back gun control.
The Clinton/Gore administration also signed the environmental agreement, the Kyoto Protocol which also was popular in the region.
I think it's more to do with just the fact that Dubya was seen as a hick and Clinton was very popular in the Northeast, than it is to do with these specific issues.
Re: "hicks", Clinton was rather unique in his ability to appeal to Northeastern suburbanites (with his Yale Law/Rhodes Scholar pedigree) while retaining a good share of the "bubba" vote.
