Explanations in Psephology

What qualifies as an "explanation"? Specifically, when will a statistical analysis explain why candidate A lost the election to candidate B?

Good explanations have a variety of characteristics (it's independent of the method, it's contrastive, social, etc.). The late Cambridge philosophy professor Peter Lipton defines an explanation (as quoted in arXiv:1811.03163)

To explain why P rather than Q, we must cite a causal difference between P and not-Q, consisting of a cause of P and the absence of a corresponding event in the history of not-Q.

The question I'm pursuing (implicitly, through a number of posts) is "Why did Trump win 2016?" The first puzzle: will this generate the same explanations as "Why did Clinton lose 2016"?

There are many variants on these questions which may be worth considering:

• What could Clinton have done differently to win 2016?
• What did Trump do (as opposed to [generic Republican candidate]) which contributed to winning 2016?
• Could a generic Republican candidate have won 2016?
• Could a generic Democrat have defeated Trump in 2016?

And could we rank how decisive each factor in the answers contributed to the outcome?

All of these questions raise different answers, particularly since we're focusing on different actors. For our purposes, understanding how the election of 2016 unfolded as it did, all of these questions may be worth investigating.

But What's a "Good Explanation"?

The second puzzle is what qualifies as a "good explanation". Lets try to examine a few (hypothetical) propositions, and see if they qualify as "explanations".

Proposition 1. If 50%+1 of voters who voted for Obama in 2012 and Trump in 2016 had changed their vote to Clinton in 2016, then Clinton would have won the election.

This gives us a path to victory, but it does not illuminate why Obama-Trump supporters jumped ship from Obama to Trump. As Lipton phrased it, this gives us knowledge but not understanding. We do not understand voter "issue preferences", to borrow a game theoretic term.

Proposition 2. Clinton didn't alter her campaign sufficiently in 2016 compared to her past campaigns.

This explanation gives understanding why she lost, but it is incomplete or not fully fleshed out...depending on what question we're really trying to explain. Proposition 2 explains why she lost 2016 partially, we would implicitly need to explain that "typical campaigning" didn't work against Trump (which hardly seems like something worth explaining to anyone who lived through it).

How could we empirically test this proposition? This is an orthogonal concern: providing evidence for an explanation. It is worth pondering, though, what data would suffice to merit this explanation.

Concerns for proof withstanding, as an explanation, proposition 2 has the quality of understanding and some flavor of causal reasoning.

Proposition 3. Johnson acted as a spoiler candidate, particularly among swing voters.

Explanations, like proposition 3, tend to sound more like excuses. How can we rigorously test such a proposition? How can we avoid fooling ourselves?

There is a clear counter-factual claim we could make, premised on proposition 3, that: had Johnson not run, Clinton would have been President. So proposition 3 qualifies as an "explanation" per se, but there are lurking factors hidden beneath it...why did Johnson get so many votes? How could Clinton have campaigned differently?

But that's a story for another day...