Donald Trump is still among the leaders for the Republican nomination for president, raising a question about how a person could be so liked when his primary method of communication appears to be insulting people.

Denigrating people seems like the last way to get popular, but when you know the social psychology of insults, it becomes easier to explain the Trump phenomenon.

Research shows that one of the primary reasons to denigrate people is to signal membership in a group: They are out, so you are in.

People are always looking to belong, and Trump may represent, for some people, a particularly attractive membership opportunity. He is clear about what “his kind” of people are: the winners, the big men on campus.

When he insults people as not having these qualities, he is providing an opportunity for others to affirm themselves by joining him in the insulting chorus.

They can call back to him by being insulting to the losers, too. It becomes a signaling contest.

Humans engage in this type of behavior all the time, insulting people while other people are watching, chirping on Twitter and at rallies, looking for their groups.

One of my favorite social psychology experiments makes the point: Students in fraternities and sororities who wanted to signal their loyalty were especially likely to denigrate people from other fraternities and sororities by judging them as “foolish” or “unintelligent” if the insults were public.

The insults are not for the insulted but for the group calling out to them.

This process only works if it is linked with warmth within the group. On Twitter, Trump is friendly and chatty with people who support him, especially if they try to get his attention by insulting nonbelievers.

“Trump pummels his opponents — and the press,” said one recent tweet from someone named John to a few hundred followers — and Trump retweeted it to 5.75 million. He commonly quotes ordinary folks’ tweets and says “Thanks!!!!” to them as if they were his best friends.

Look at the entirety of Trump’s speeches. The sound bite gets a lot of negative media attention, but in between those moments he is personal, leaning forward on his podium, laughing as if he were talking to people he knows at a dinner party.

He has some gestures that look as if he is almost embracing the crowd, gathering them in.

His supporters won’t ever abandon him, because “club” members are forgiving of their leaders.

A recent set of studies affirms this: People don’t mind if the captain of their favorite soccer team loses his temper, yelling and cursing at the referee. In fact, they like it.

If the captain of another team behaves this way, people find it unseemly. It’s all a matter of which group you are in — the “in” group or the “out” group.

What might stop Trump’s current magic? One way that the denigration/friendship cycle could end is if he insults too many people and it becomes confusing just who is in his circle.

This type of mistake is likely, because he is inconsistent in his affections. He has registered in both political parties, after all, and seems to have held every possible political position.

It is always a sad day when you realize the friend who is so gossipy and fun with you, always with a snarky comment to make you laugh about everyone else, is also similarly snarky to other people about you. It makes it so that the us-against-them bond becomes more tenuous, and group sentiment dissolves.

So, the best thing for Trump detractors would be for him to keep talking until he shirks his fraternity and shatters the illusions of friendship to such an extent that he is left essentially alone, a group of one against everyone else.

Julie Irwin is a professor in the Department of Marketing in the McCombs School of Business at the University of Texas at Austin.