As we saw in Florida, any factor which impairs the ability to repeatedly read a ballot during a recount is going to hurt the majority candidate in that batch more than the minority candidate in that batch, simply because the majority candidate has more ballots subject to being tattered, etc.
Don’t forget about King County, WA and the election that inserted (yet again) a dem gov. They kept recounting and recounting until they got the answer they wanted. Then the recounts ended.