Good point, but a mid-term appointment would only last until what would have been the end of Torricelli's next term in office.
I'm not sure McGreevey will be able to find someone who is willing to sit in the U.S. Senate for two months and then have to run for re-election. Although Newark mayor Sharpe James is a possibility -- I don't think I've ever seen a dumber human being than him wearing a suit and tie every day.
It'd be a calculated risk for the Democrats, to be sure. They would have to determine which option gave them the better chance to retain this seat: a damaged Torricelli vs Forrester, or a "clean" Democrat with some possible advantages that might go with a two-month incumbency. Considering that New Jersey leans heavily Democrat, it might make sense to bite the bullet and dump the controversial Torricelli. After all, if the scandal-ridden Torricelli is out of there, a lot of the impetus for Forrester's campaign is deflated. I don't know enough about New Jersey politics to comment as to whether there are any possible attractive Democrat candidates for such a maneuver.