With Trump, the rules have changed. So far, he has proven to be largely immune from attack, and also a master killer himself, with a unique political arsenal. With a few months to go before voters vote, Trump has squashed the poll numbers and personas of a host of his rivals, without resorting to significant traditional opposition research, paid media, or surrogates. He simply uses Instagram, Twitter, and his virtually unlimited access to the news media to unsheathe his sharp tongue, cutthroat sensibility, and unerring perverse humor. And Trump can shift to kill mode without strain or hesitation.

From the get-go of his entrance in June, Trump has engaged intuitively in kill-or-be-killed tactics. He’s shown a hair-trigger impulse for payback, game to needle, insult, or slam rivals from all points on the poll spectrum, whether they be purported chief challengers such as former Florida Governor Jeb Bush, or subtler contenders struggling in the polls, such as South Carolina Senator Lindsey Graham and former New York Governor George Pataki. It does not seem to be a coincidence that three candidates who have seen their nomination prospects rise of late (Texas Senator Ted Cruz, Ohio Governor John Kasich, and retired surgeon Ben Carson) have avoided tussling with Trump, although the billionaire did participate in a brief scuffle with Carson last week (after which Carson apologized). On Friday, as noted, one of Trump’s most energetic brawlers, Perry, became the first candidate to leave the race.

Months away from Iowa, Trump has clashed with more rivals than the other 16 candidates combined. Campaigns typically don’t go negative early—they like to spend time introducing their candidates to the voters in a positive way, so they’ve got a foundation of goodwill before things get ugly. Trump is already well known by the public, so he has been free to strut his stuff—the buoyant and the bullying. In Trump’s view, of course, he’s just defending himself. “They attack…me first and I hit them back and maybe even harder than they hit me,” he explained over the weekend.

When media outlets and pundits exclaim that he’s gone too far, Trump is never sorry, never accepts any blame. Unlike other candidates caught in the Internet glare of controversy, Trump doesn’t do the deer-in-the-headlight cringe, nor does he apologize. When asked about his favorite Bible verses or challenged on his remarks about debate moderator Megyn Kelly and rival candidate Carly Fiorina, Trump hasn’t flinched, even when giving answers that some listeners find incredible. When he becomes aware he has stepped over the line (sometimes thanks to the counsel of his daughter, Ivanka), he knows how to minimize the damage by bluffing his way out the other side. And his capacity to generate news coverage and controversy gives him an unprecedented ability to change the subject and turn the page if he missteps.

In addition to his many imperious iterations of “they attacked me first,” he’s now, somewhat ingeniously, embracing his rough-and-tumble rep. “I don’t think it matters this time,” Trump said this weekend in Iowa. “We’re tired with this nice stuff. We need people that are really, really smart and competent and can get things done. We need people with an aggressive tone and we need people with tremendous energy and I’m your candidate.”