If a Republican pollster can't have Trump any closer, he's doomed. However, I think this might actually be the margin Joe Biden wins Pennsylvania in November. He'd be winning by more if the election was held today, but (I assume) the numbers will somewhat tighten towards the end of the campaign.
Why do people assume this? If anything Biden’s lead could get bigger.
Maybe I'm wrong, but Trump I believe Trump has a floor of 45-46% in Pennsylvania. Even if Joe Biden wins nationally by 2008 levels, Pennsylvania will be more like 2012 margin-wise (Biden doing better in suburbs and worse in some rural WWC counties compared to Obama eight years ago).