Judgment day is nigh. Like it or not America will end up with President Hillary Clinton or President Donald Trump. How to choose?We know who Hillary and Donaldare.Both have well-documented histories; journalistshave plumbed those pasts and analyzed their characters. But what would theydo?

To answer that, we “war gamed” their presidencies. How would Trump and Hillary respond to a murderer’s row of foreign and domestic crises? What moves would they make on immigration, taxes, healthcare and the...