How economically important is an inspirational president?

Mark Thompson, a loyal MR reader, writes:

I'm wondering if you would be willing to address the question of whether and how much of an economic effect a President can have simply by making people feel good about themselves.

Mark's own answer is here.  I'll say that the personality of the president matters most in models with multiple equilibria.  There can be a high-output equilibrium and a low-output equilibrium, and perhaps the mood and demeanor of the President can shift the country from one to another.  "Good morning, America!" etc.

But are these models true?  I've never seen general evidence for their applicability, although I recall Ronald Reagan's smile and Jimmy Carter's pessimistic sweater.  Furthermore GDP growth rates are statistically indistinguishable from a random walk (NB: in a test with low power), which doesn't help these models either.  Since the temperament of the politician seems to persist over time, you would think that patterns in GDP would be more predictable than they are.  But they aren't.

Note that if you buy into multiple equilibria models of business cycles, it is a matter of great importance when the Fed acts to stimulate the economy.  It would probably be too late now because the pessimistic mood already has set in.  But more vigorous action, say a few months ago, might have kept spirits high.  That's if you buy into those models.