He won't be winning many votes back, as those who like Snowden likely didn't vote for him, but he might be considering winning some votes "forward", as it's not likely Republicans would vote for Biden just to spite Trump for pardoning Snowden - who is increasingly irrelevant anyway, he did what he did and by now nobody cares about his personal destiny too much and it's not likely there's a chance to punish him anyway. But if he could win some independents who are on the fence - that would be nice.