You can find the brief here. This time the “evidence” of voter fraud comes from statements of members of Congress (see brief at 15-17), most of them related to unproven anecdotes of voter fraud as well as types of voter fraud (such as mail in balloting voter fraud allegedly done in the names of dogs) that an in person voter id law would do nothing to prevent.
[Disclosure: I filed an amicus brief supporting petitioners in this case.]