 First, I would say vice presidential choices always matter. The kind of political science consensus that they don't is based on methodology that I think is terrible. The vice president choice tells the story about who you are. So it informs how people think of the top of the ticket. So it always matters. Now, if Harris is the nominee because American politics works, and the same way it was when Obama was the nominee. Remember, Joe Biden wasn't picked as Obama's vice president because he was the most qualified.