"To be perfectly clear, from my own perspective, Kaine's whiteness and maleness adds nothing to his appeal, while the alternative of continuing to break down the white-male stranglehold on the presidency has a lot of appeal. But if we are considering the selection in hardheaded political terms, the fact is, Donald Trump is appealing to millions of voters on the basis of demographics—specifically, he is exploiting the fear among whites and men that social change is leaving them behind. If Clinton had a ticket without a white man, many of these voters would see it as a symbol of this change. Kaine's presence might help reassure them. If your concern is to reduce the calamity of a Trump presidency, neutralizing the main source of his popularity seems wise."
Jonathan Chait in New York reacts to Hillary Clinton naming Tim Kaine as her running mate.