Try to read the sentence without the part in the middle, i.e.,
- Nessuna legge elettorale porterà nulla di buono.
- Nessuna legge elettorale porterà qualcosa di buono.
Read in that way, the second one looks more correct. An English translation in the sense of "meaning" (i.e. not a "word-by-word" translation) would be
- There is no election law that will bring nothing good.
- There is no election law that will bring something good.
while, as Walter Tross suggested, there is a third opportunity which is
Nessuna legge elettorale porterà alcunché di buono.
which is also translated as
There is no election law that will bring anything good.