PA, bite me.
They're both pretty similar, but Josh Shapiro is the single most overrated candidate this cycle thus far. He's a very partisan Dem who has very little demonstrated crossover appeal, overperforming Biden by 3 against a poorly known opponent. In addition, Tom Wolf is even more unpopular than Whitmer is right now, and he's served alongside him and has to defend his record. It's just not realistic to think he's going to do much better than Whitmer.
It's not that Shapiro is strong but that Mastriano is an insane extremist. With the suburban-heavy environment midterms usually are, that could be a tough sell.