It seems like almost everyone (and I include myself in this) feels that they are qualified to give authoritative advice on who a major party nominee should choose as a running mate. If you bring up the topic, people who are very reticent to offer an opinion on health care or transportation policy will suddenly get very chatty.
I’m not saying that some people don’t have well-informed opinions and even some good solid advice that the nominees would be wise to consider. But, if you really think about it, this is a bit like telling someone who to hire as their personal assistant or even their nanny. It’s not that the job of the vice-presidency is really comparable to those jobs. It’s that there is a personal chemistry and comfort component involved that we’re not in a good position to judge. A veep candidate can check all the boxes and look great on paper but actually be a very poor fit for reasons we don’t understand.
And we’ve seen presidential candidates make this kind of mistake themselves. Dan Quayle was young and photogenic and helped Bush shore up the conservative right. He looked like he’d help Poppy Bush in the competitive Midwest. But he was a bad candidate and an even worse vice-president, and he certainly never fit in in Bush World. John Edwards looked great on paper, but a closer look revealed something ugly. Sarah Palin couldn’t stand even modest scrutiny but she convinced Bill Kristol that she’d be a great running mate.
Ultimately, picking a running mate is a very personal decision. And it’s a difficult one because just having to make it offers all kinds of perverse incentives. You want someone who could run the country if they needed to, but you’d also like them to help you win. You want someone who would be a good and loyal solider in your administration. It’s easy to begin thinking too much about one of these factors at the expense of the others. A loyal running mate might not be a good leader. Someone who helps unite the party might ultimately divide it if they insist on maintaining their power base and independence. You could pick up votes with an important constituency but wind up with a candidate who has big skeletons in their closet, or who simply isn’t prepared to be president if need be. Maybe the best candidate is a senator from a state with a governor from the other party, and selecting them could cost you control of the Senate.
There are so many considerations, and so may ways to screw up this decision.
The first-do-no-harm advice is probably the best.