Sorry, but no study or academic treatise (!!) is going to tell you what's happening right now.
If you have any awareness at all of what's going on in the country today, you'd know that Governor Tim Walz has won over more than just the state of Minnesota. I believe that he'll add more to the ticket than any of the other VP candidates would have added.
He certainly performs better than they do in front of audiences. Even Mayor Pete, excellent as he is, can't fire up a crowd like Walz does with policy stuff as well as homegrown folksy stuff. In political-speak, this is gold. And no "academic treatise" is going to prove that with statistics.