Donald Trump speaks at a Pearl Harbor Day Rally on December 7, 2015, in Mt. Pleasant, South Carolina. (Photo: Sean Rayford/Getty Images)

The pattern has become numbingly familiar: Donald Trump says something inappropriate and disrespectful about one of his opponents, a media personality, or an entire group of people. With each new offense, analysts assert that this boorish behavior will cost him support. But the anticipated drop in his poll numbers never materializes.

What does it say about his supporters who, going by all available evidence, don't care that he's a jerk? Newly published research from Germany gives us a clue.

It finds people whose self-image isn't tied closely with moral concerns view rude candidates as more competent than respectful ones. To them, a disrespectful demeanor conveys capability.

Trump's boorishness may be more calculated than we realize.

That's the conclusion of a research team led by the University of Hamburg's Christina Mölders. Not surprisingly, their research finds that voters judge candidates on both their competence and warmth—that is, how effective they seem, and how well they get along with others.

But, the researchers write in the journal Political Psychology, the relative weight voters place on those two factors depends in part on whether they "emphasize morality in their self-definitions."

If you perceive yourself as a caring, compassionate person—or at least aspire to become one—cordial, respectful candidates tend to appeal to you. If you don't derive your identity from such factors, you're more likely to vote for the tough, abrasive guy.

The researchers looked at the 2013 German elections, which were contested by parties led by Prime Minister Angela Merkel and opposition leader Peter Steinbrück. Merkel, they note, "hardly ever raises her voice, even in the face of personal attacks."

Steinbrück, on the other hand, "called his colleagues 'crybabies' and referred to politicians he did not appreciate as 'clowns.' Linguists labeled his frank and disrespectful method as 'calculated churlishness.'"

Sound familiar?

The researchers honed in on the source of such candidates' appeal in three studies, one of which featured 329 German adults. After participants read and reacted to vignettes in which a political candidate confronted an opponent in either a respectful or disrespectful way, they filled out a shortened version of the Self-Importance of Moral Identity Scale.

Participants were asked to imagine a person who embodies various moral characteristics, including being caring, compassionate, and friendly. They then indicated "the extent to which they would like to be such a person." Specifically, they rated (on a one-to-five scale) their level of agreement with such statements as "Being someone who has these characteristics is an important part of who I am."

The key result: People who scored low on "moral identity"—that is, those whose sense of themselves was not based on the notion of being a good human being—rated candidates who behaved respectfully as significantly less "agentic" than their rude opponents. Agentic, according to one definition, refers to a leader who demonstrates "assertiveness, competitiveness, independence, courageousness, and is masterful in achieving their task at hand."

So, among that portion of the population, rudeness signals leadership strength.

Now, Steinbrück's party lost decisively, suggesting that, among the electorate as a whole, his abrasive language and demeanor led to an "overall backlash effect."

"Politicians thus damage themselves ... by communicating disrespectfully," the researchers conclude.

But don't breathe that sigh of relief just yet. Mölders and her colleagues go on to note that voters' decisions are influenced by the specific circumstances in which an election takes place.

"In times of crisis or conflict, when action orientation is needed," they caution, "voters might seek politicians who are very self-confident, assertive, and active, and simultaneously be more forgiving of interpersonal weaknesses."

So politicians who behave badly have a built-in advantage with one slice of the electorate, and, depending on the concerns of the moment, their behavior may be only a secondary factor in the minds of many other voters.

Trump's boorishness may be more calculated than we realize.

Findings is a daily column by Pacific Standard staff writer Tom Jacobs, who scours the psychological-research journals to discover new insights into human behavior, ranging from the origins of our political beliefs to the cultivation of creativity.