Rodney has more than sufficient time to raise his profile and to fix his credentials. Sitting on his laurels and name aren’t going to cut it.
There are two major threats to Frelinghuysen's seat in Congress:
1. Out-migration of wealthy Republican voters from New Jersey. His district has a lot of them.
2. The abject stupidity of many conservatives in his district (you'll find plenty of evidence right here on this thread) who are delusional enough to believe that a candidate who runs on a middle American GOP platform or a Rust Belt "Make America Great Again" platform has a snowball's chance in hell of winning in his district.