For months Republican US presidential hopefuls traded insults such as “dummy”, “jerk” and “loser”. Then, party front-runner Donald Trump repeated a supporter’s description of Ted Cruz as a “pussy”.

With the

contest for the party’s nomination moving into South Carolina and the stakes rising, it is possible the most disparaging discourse of the November 8 election campaign is yet to come.

The epithets may be characteristic of schoolyard bullies, but there is some evidence that candidates are revelling in the attention they draw. The harshest attacks elicit the biggest responses at rallies, on the internet and on cable TV.

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Trump, the billionaire former reality TV star, sent a New Hampshire rally into a frenzy on Monday when he repeated the term “pussy” shouted by a person in the crowd, effectively questioning Cruz’s manliness. Trump went on to win the state’s primary the next day, ahead of the third-place Cruz by a three-to-one margin.

“It’s one of the reasons I won. You have to be yourself,” Trump said in a television interview on NBC’s Today show. Trump later promised to clean up his foul language and to be more presidential.

History suggests the language could turn even more coarse in the run-up to next Saturday’s Republican nominating contest in South Carolina. It was there that US Senator John McCain of Arizona was accused in 2000 of fathering an illegitimate African-American child, and former Massachusetts Governor Mitt Romney in 2008 of supporting polygamy.

“These adults are acting like elementary children,” Leslie McRobbie, a former fifth-grade schoolteacher from New Hampshire, said of this year’s Republican contenders.

President Barack Obama, a Democrat, this week spoke of the “snark” that characterised a Republican race of the past when he recalled that Ronald Reagan was described by rivals as an “unshapely man” and a “yahoo” before his election as president in 1980.

Coming off the first nominating contests in Iowa and New Hampshire, the seven remaining candidates for the Republican nomination are under pressure either to break away from the crowd or prevent others from doing so.

Insults can foster that.

Former Florida governor Jeb Bush, mocked more than once by Trump as a “low-energy” candidate, has since retaliated by tweeting that Trump was “not just a loser”, but also a “liar and a whiner”, The put-down was re-tweeted nearly 3,000 times and “liked” by more than 4,000 users.

Cruz, responding to Trump’s decision to skip a Fox News-hosted Republican debate, branded his rival “Ducking Donald” and sponsored a special edition filter on picture sharing app Snapchat that featured a blond-haired duck with an exaggerated pout meant to represent the property mogul.

“When we create so much of the modern campaign around the characters that are running, and not on the subjects, the natural by-product of that is calling people names,” said political scientist Michael Artime.

Artime said that while bickering and name-calling have always existed in elections, this cycle has seen a notable uptick in the negative.

“In the past, if somebody would’ve said what Trump said the other night, that would have been a very damaging thing to their campaign,” Artime said. “The kind of politics we get is kind of the politics we deserve,” he said.

While many have gleefully or indifferently watched as candidates hurled barb after barb, others have condemned it.

“Bullying can be highly instrumental and used for social climbing,” said Bob Faris, associate professor of sociology at University of California-Davis, who studies aggressive behaviour in adolescents. “And it works,” he said, “provided that kids target the right kids.”

For Trump, perhaps the most blustery of the candidates, the target is constantly changing, his numbers remaining constant in the opinion polls while he assails rivals for being “stupid”, “weak” and “pathetic”.

“He does look like a bully,” Faris said. “Donald is a whole new development. I can’t think of a candidate like him.”

Presidential historian Mike Purdy, however, cites a precedent in the late Republican President Theodore Roosevelt.

“Roosevelt loved more than anything else to be the centre of attention, and he had a huge, huge ego,” Purdy said. “They both have a certain amount of ego. They both have trouble controlling their mouths,” Purdy said, likening Roosevelt to Trump.

Purdy said Roosevelt called his onetime ally William Howard Taft a “fathead” during the 1912 presidential campaign, and went on to say then-rival Taft, seeking re-election at the time, had the “brains of a guinea pig”. Neither won the race.

Purdy noted the attacks also came at the expense of substantive political discourse.

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“They’re incredibly personal attacks, and they’re not just attacks just on somebody’s position, they’re attacks about personal characteristics,” he said. “That is part of the civility I think we need to recapture.”

On Friday, Trump suggested he agreed.

“I do this for effect,” Trump said of his foul language in an interview with WOR Radio in New York. “As we get closer, you will be shocked at how presidential I will be. You will be very proud of me.”