1. Vice-presidential picks, unless they are truly disastrous (Eagleton, Palin), don't count much in elections. But they are important for unifying parties and allowing them to function as coalitions.

2. The 2016 election is instructive: Trump's pick of Pence was a smart move: it ensured the enthusiasm of evangelicals. They would have one of their own at the table. By contrast, Tim Kaine didn't have enough of a political profile distinct from Hillary Clinton to add anything

3. Some thoughts on why Elizabeth Warren as running mate would help unify the Democrats and is also the best person for job https://www.thenation.com/article/politics/biden-warren-vice-president-pick/