But as Trump’s many foes are learning, it’s a mission fraught with danger—usually leaving the assailant a bloody mess and The Donald licking his restless chops.

So beware, candidates. Here’s an abbreviated history of the perils of attacking Trump:

On Tuesday, the free-market advocacy group Club for Growth—no stranger to brutal campaign tactics—announced a $1 million ad campaign in Iowa to destroy Trump. The first commercial, a litany of the real estate mogul’s past liberal positions, concludes: “He’s really just playing us for chumps.”

Pointing out any other candidate’s flagrant flip-flops would hurt, especially with Iowa’s seasoned voters. But Trump has an uncanny ability to turn the conversation to his own advantage. So he took to Twitter to paint the Club for Growth as a bunch of chumps—a “little respected” outfit that turned on him after soliciting a $1 million contribution. “Now they are spending lobbyist and special interest money on ads!” he added for good measure.

Likewise, two weeks ago Jeb Bush traveled down the flip-flop route with his own ad, a video with clips of Trump praising Democratic frontrunner Hillary Clinton and supporting a single-payer health care system. It seems voters were more impressed by Trump’s earlier brush-off of Bush with two words—“low energy”—that brutally captured what everyone had been saying about Bush behind the one-time front-runner’s back.

In the days since Bush went on the attack, Trump’s poll numbers have ticked up while Bush’s have gone down. (Recent polling has Trump in the 27-33% range among GOP voters, with Bush in the 6-8% single digits.)

In July, former Texas Governor and presidential candidate Rick Perry called Trump’s campaign a “cancer on conservatism” that should be “clearly diagnosed, excised and discarded” before it destroys the Republican Party. “He offers a barking carnival act that can be best described as Trumpism: a toxic mix of demagoguery, mean-spiritedness and nonsense that will lead the Republican Party to perdition if pursued,” Perry said.

Perry was merely vocalizing what most veteran GOP strategists think about The Donald—especially after Trump’s racist remarks about Mexican immigrants, followed by a rude dismissal of war hero Senator John McCain. No matter. Last week, Perry became the first Republican presidential candidate to drop out of the race.

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It probably didn’t help his struggling campaign that Trump viciously and brilliantly dredged up Perry’s 2011 “oops” moment when he couldn’t recall the third federal agency he wanted to eliminate. In July, Trump tweeted this: Perry “should be forced to take an IQ test before being allowed to enter the GOP debate.”

Barely registering in the polls, and clearly seeing nothing to lose, Louisiana Gov. Bobby Jindal has called Trump a “narcissist” and “egomaniac” who has gone bankrupt more times than any major corporation in the last 30 years. Trump shot back with his familiar “loser” label, customized for the governor: “Bobby Jindal did not make the debate stage and therefore I have never met him. I only respond to people who register more than 1% in the polls.”

Jindal insisted to Fox News last week that his Trump attacks are working and that he’s climbing in the Iowa polls. Maybe. But Jindal, who had to sit at the “kids table” for the first debate, won’t be on the main stage on Wednesday night either.

The lesson from all this? Maybe the only one who can take down Trump…is Trump