Ping for your thoughts and relevant data
But all else might not be equal this year. Lautenberg is 84 (and an old 84 at that). Zimmer seems to be a fiscally-conservative, socially moderate sort of Republican with some solid credentials. He wrote "Megan's Law" and has been a champion of government reform. He also went to Yale Law, but I'll try not to hold that against him. I'm a little surprised he's not running closer to Lautenberg, but it is New Jersey after all, and he is one of the Senate's most liberal members.
However, if McCain runs strongly in NJ, which polls are suggesting might be the case, a little coattail effect would not be out of the question, especially if McCain comes to the state personally. I wouldn't have believed that possible two months ago, but there it is.