All the participants were asked to rate how unethical it was to tell the falsehoods. But half the participants were first invited to imagine how the falsehood could have been true if circumstances had been different. For example, they were asked to consider whether the inauguration would have been bigger if the weather had been nicer, or whether Mr. Trump would have removed the bust if he could have gotten away with it.

The results of the experiments, published recently in Personality and Social Psychology Bulletin, show that reflecting on how a falsehood could have been true did cause people to rate it as less unethical to tell — but only when the falsehoods seemed to confirm their political views. Trump supporters and opponents both showed this effect.

Again, the problem wasn’t that people confused fact and fiction; virtually everyone recognized the claims as false. But when a falsehood resonated with people’s politics, asking them to imagine counterfactual situations in which it could have been true softened their moral judgments. A little imagination can apparently make a lie feel “truthy” enough to give the liar a bit of a pass.

These results reveal a subtle hypocrisy in how we maintain our political views. We use different standards of honesty to judge falsehoods we find politically appealing versus unappealing. When judging a falsehood that maligns a favored politician, we ask, “Was it true?” and then condemn it if the answer is no.

In contrast, when judging a falsehood that makes a favored politician look good, we are willing to ask, “Could it have been true?” and then weaken our condemnation if we can imagine the answer is yes. By using a lower ethical standard for lies we like, we leave ourselves vulnerable to influence by pundits and spin doctors.

In this time of “fake news” and “alternative facts,” commentators worry that people with different political orientations base their judgments of right and wrong on entirely different perceptions of reality. My research suggests an additional concern: Even when partisans agree on the facts, they can come to different moral conclusions about the dishonesty of deviating from those facts. The result is more disagreement in an already politically polarized world.

Blame the human ability to imagine what might have been.