From my understanding, there were two conflicting laws regarding appointments of senators and elections. I mentioned one previously, there couldn't be Gubernatorial and Senatorial elections on the same day.
There was a Dem assemblywoman (state congress), who filed suit to hold the election the same day but was ruled against by the state supreme court. The Dems were basically hoist by their own petard because they were the one's who set the election law.
NJ is a very odd bird politically. There is (or was) a solid, independent (not Republican) Conservative party about 50,000 - 75,000 that may use chicken innards. There is a very healthy Libertarian presence in NJ. There is also a strong collegiate political scene used by the socialists from Democrats to Greens. Finally, the Dems have a 750,000 voter advantage over Republicans.
These are numbers from various news organizations.