This mental fallacy explains who your friends are voting for in the primaries

The instinct to reduce cognitive dissonance explains why nearly nobody wants to admit that the candidate they like best might not do so well in the general election.

For the past few weeks, my Facebook feed has turned into a peculiar kind of political battleground: My friends who support Hillary Clinton are duking it out with my friends who support Bernie Sanders. This much is unsurprising. After all, a lot of my friends are very political, and many make their living as pundits or political scientists. But one thing does strike me as odd about the conversations they're having: Nearly all of them think the candidate they like best also happens to have the best chance of beating the Republican nominee.

In fact, nearly all the Clinton supporters I know believe Sanders is too far out of the American political mainstream to win the general election. Meanwhile, nearly all the Sanders supporters retort in kind: They argue that the base isn't excited enough about Clinton to mobilize the core Democratic constituency, and that she is too disliked by moderates to win over a lot of swing voters.

But why should people's views dovetail in this neat way? Is there any good reason why a normative preference for, say, universal health care and free college should also give you good reason to think Sanders would do better than Clinton at beating Donald Trump?

Not really.

Instead, the likely explanation lies in one of the most powerful mental fallacies to which human beings are prone: the desire to reduce "cognitive dissonance."

We experience cognitive dissonance when we have some belief or value about the world and then encounter new information that seems to stand in tension with it. Here's a straightforward example. Imagine I believe that my friend Andrew is a very kind person, but then I hear that he has been extremely rude to somebody at a dinner party. This creates cognitive dissonance: The clash between my general belief that Andrew is a good person and the specific evidence that he is a jerk would likely distress me.

Now, the way most human beings deal with cognitive dissonance is to try to reduce it. Psychologists have found that instead of giving serious consideration to the possibility that Andrew might not be as kind as I thought, I am much more likely to discount the new information about him. Perhaps it simply isn't true that Andrew was being rude, I will tell myself. Or perhaps he had good reason for what he did?

This same process of reducing cognitive dissonance is going on with a lot of my Facebook friends — and with political partisans all over the country — at the moment. People who like Sanders's (or Clinton's) political positions and then are presented with evidence that he (or she) may not be a good general election candidate experience cognitive dissonance. Instead of reassessing whether they really should support Sanders (or Clinton), they try to convince themselves that there must be something wrong with the evidence. Sanders (or Clinton), they insist, is more likely to win a general election after all.

I must admit that I've been pretty pleased with myself over the past weeks to have avoided making the same mistake. "Aren't I smart to have avoided so obvious a pitfall?" I thought to myself.

But what about the general election? I don't have nearly as strong a preference about Sanders or Clinton as I do about either of them versus Trump or Ted Cruz or Marco Rubio. And, like many pundits, I had assumed that the Democrats were very likely to prevail against the Republicans this year. The GOP, after all, is in the midst of a populist fever, alienating key demographics with abandon as their main exponents are railing against everyone from Muslims to Mexicans. Surely, I thought, a party whose leading exponents are now identified with such repugnant views can't possibly take the presidency.

Then, with a start, I realized what should have been obvious to me all along. Isn't it possible that I, too, have fallen foul of my own cognitive biases? What if Bernie supporters are right that Hillary is too tainted and uninspiring to make a good general election candidate, while Hillary supporters are right that Bernie is too far out of the political mainstream to become president? Is my belief that Democrats are very likely to win in 2016 itself owed to my unconscious desire to reduce cognitive dissonance?

This post is part of Polyarchy, an independent blog produced by the political reform program at New America, a Washington think tank devoted to developing new ideas and new voices. See more Polyarchy posts here.