In 98, coattails mattered since Engler beat Fieger by 25%. In 02, there were no coattails at all in Granholm's 4% win.
That would not be correct.
Bush nationalized the state elections in '02 with a platform that centered around WOT, judges, and tax cuts. By nationalizing the elections people that might opt Dem locally went Republican. In the '04 elections we saw that nationalization of the elections continue, and it is largely why '06 is considered to be a bad year for Dems even though midterms are supposed to be good for the party out of power. By making these referendums on the head of the ticket and the platform states that vote Rep are now far more likely to vote for a Rep in the Senate, and vice versa.
In '04 specifically Bush's coattails helped in Alaska, South Dakota, and a few other states that were very close. Some of these candidates were slated to lose, and barely squeaked by as it was. The high turnout for Bush, and '02 the nationalization of the platform, helped coast many of them over the finish line.
But New Jersey has been a solid blue state recently. Perhaps the understanding of how corrupt the Democrats (Torricell, McGreavy) are has sunk in there.