Johnny is an unhappy voter. He says, “I can’t stand Trump. But I’m not crazy about Harris either. So I’ll either vote for a third party, even though I know they can’t win, or I just won’t vote for president.”

Johnny’s inclination to cast a “protest vote” (or nonvote) sounds reasonable. Is it? Johnny’s vote is extremely unlikely to swing the outcome. Why shouldn’t he then just protest-vote if that feels right to him?

Well, suppose there’s a bloc of 10,000 “Johnny voters” in Johnny’s state who all are unsatisfied with Harris but hate Trump. Maybe half dislike her because they think she’s too far left, and half think she’s too conservative. Regardless, this bloc probably will swing the state’s outcome: Trump likely has an edge of 5,000 votes among the state’s other voters, so if the 10,000 Johnny voters all vote for Harris, she wins. If the 10,000 Johnny voters all protest-vote or abstain, Harris loses.

Since Johnny dislikes Trump more than Harris, he wants the 10,000 Johnny voter bloc to not protest and vote for Harris. If Johnny believes in the golden rule – and most of us do – and if he thinks the other Johnny voters should vote for Harris, then Johnny should do the same thing himself.

So, why wouldn’t Johnny do this? Why might his intuition lead him astray here? Why might he, and others, have a protest vote bias, a tendency to protest vote when they shouldn’t, according to their own values? There are several reasons.

The first is a misguided use of a boycott heuristic. A heuristic is a rule-of-thumb that we follow to avoid the cognitive and time costs of thinking through all decisions carefully. Heuristics are usually helpful but can lead to trouble because we use them on autopilot. They don’t work well in all circumstances we face.

A boycott heuristic – a rule-of-thumb to boycott something we don’t like – is indeed often completely sensible. If there’s a restaurant in town with a reputation for being discriminatory, or just for being slow to get the food out, don’t go to it, and maybe you’ll help pressure it to shape up.

But when you enter the voting booth on Election Day, boycotting the viable candidates isn’t going to help. One of them is going to win, whether you like it or not. A boycott in this context doesn’t help you achieve your goal of eliminating or improving a bad actor. So the intuition to boycott here is misguided.

The second cause of protest vote bias is omission bias: the bias toward favoring mistakes of inaction (omission) over mistakes of action (commission). Since mistakes of omission can easily be as bad or worse than those of commission, this bias can lead to bad decisions.

Omission bias can help explain vaccine hesitancy. If you choose to get vaccinated and this led to a health problem, that would be a mistake of commission. Not getting vaccinated and then having a problem would be a mistake of omission. Many people seem to prefer the latter.

Voting for Harris could be a mistake of commission, while not voting for her risks “merely” a mistake of omission. As a result, omission bias could make people too prone to abstain from voting for candidate.

A third cause of protest vote bias would occur if Johnny objects to my premise above that he dislikes Harris less than Trump and instead claims “They’re equally bad!” This is almost surely untrue for Johnny, no matter what his true policy preferences and values are.

But Johnny might think two quite different candidates are “basically the same” due to the human tendency to think in categories, also sometimes called coarse thinking. This is another mental shortcut that’s often useful but sometimes leads to big mistakes. Grouping distinct items in the same category can make us neglect substantial differences between these items. For example, people sometimes think about both 1 in a million chances and 1 in 10 chances as “possibilities.”

I remember during the 2000 campaign, famously seemingly spoiled for Al Gore by Ralph Nader’s third-party candidacy, I had a friend who said he wasn’t voting for Gore because he and Bush were equally bad. After winning, Bush proceeded to withdraw the U.S. from the Kyoto Protocol to limit global carbon emissions, invaded Iraq and passed tax cuts favoring the wealthy. It became very clear that those candidates weren’t at all the same. It should have also been clear before the election. It just wasn’t clear to a coarse thinker.

We will have a new president on Jan. 21, 2025: Trump or Harris. A third party is not a real option. Would it be nice to have more choices? Absolutely. Perhaps work on reforms such as fusion voting will eventually yield more feasible choices years from now. It certainly won’t happen by Election Day 2024. If you are tempted to opt out of the true binary choice you face, please be sure your decision isn’t being driven by one of the cognitive biases described above.