McGreevey definitely hurt the Democratic party in NJ. Although he shouldn't have, some people are really stupid enough to take this to heart and nail the whole party as a result. This is similar to John Street and NE Philly, but I'll post another thread about that one. It seems scandals rock the Democratic party harder than the Republicans.
Actually it's because Democrats, particularly those of the NJ variety, are extremely corrupt-- far more than Republicans. McGreevey was just another example of that corruption, plus tapes came out recently with top DNC officials in NJ laughing about how they "own" even the rich Corzine.