That's really not true anymore. That used to be the case, and it explains why a Republican like Tom Kean could win Essex County even as recently as the 1980s. The suburban areas surrounding Newark were much more conservative then.
What has made New Jersey much more "blue" since the 1980s is that those suburban areas have turned into prime destinations for wealthy New Yorkers looking to flee from places like Brooklyn. Look at towns like Montclair, South Orange and Maplewood. Suburban Essex County is just as radically liberal as Newark and Camden these days.
True. The South Orange schools are run by SJWs now.