Temperament: Has the candidate ever faced a true crisis? Do they have the equanimity to handle the erratic and unpredictable pressures of the office? How are they with uncertainty?
You'll notice a word that is missing here: leadership. We can all agree that a president should be a leader, but what does that mean? Gen. George Patton or Mahatma Gandhi? It depends on the circumstance. The word leadership in presidential politics only distracts or obscures. What a president's critics really mean when they say he "isn't leading" is that he hasn't announced that he is supporting their plan. Challengers vow to show leadership, but that amounts to little more than saying they'll magically pass the vast programs they're promising. They don't want anyone to ask the "how" question. They want you to assume that a leader can get anything done.
Rather than testing for leadership, we should recognize that leadership is actually the sum of these four attributes — and probably a few more. These attributes, unlike the vaporous leadership mantle, are more measurable qualities. We shouldn't let politicians get away with asserting they have this magical ability when we can bore down a little deeper to see whether they have these necessary and underlying traits.
I am not claiming that by looking at things this way we can produce a mathematical formula for candidates. There is no Myers-Briggs test for successful presidents. But unlike the mindless speculation over who will get the nod to be a candidate's running mate, at least thinking about these is not completely useless. In the end, searching for the answers should help bring the candidates into somewhat clearer focus.
Dickerson is Slate's chief political correspondent. On Twitter: @jdickerson