Republican presidential candidates Donald Trump (L) and Ben Carson (R) participate in the Republican Presidential Debate hosted by Fox Business and The Wall Street Journal November 10, 2015 in Milwaukee, Wisconsin
Washington (AFP) - Republican presidential frontrunner Donald Trump has unleashed a verbal assault on his nearest competitor Ben Carson, comparing him to a pedophile and saying US voters were "stupid" to believe the doctor's moving personal narrative.
It was Trump's most aggressive campaign speech yet in his bombastic run for the 2016 Republican nomination, hurling sharp insults against several rivals including "weak-like-a-baby" Senator Marco Rubio and business executive "Carly whatever-the-hell-her-name-is" Fiorina.
The billionaire real estate tycoon, 69, pulled no punches during a Thursday night stump speech that devolved into a 95-minute rant in Fort Dodge, Iowa, the state that votes first in the presidential nomination process.
He reserved his harshest criticism for Carson, already under scrutiny for details of what he has said was a violent adolescence in which he claims to have tried to stab a classmate.
Trump flipped his belt buckle up and down, ridiculing Carson's claim in his 1990 autobiography "Gifted Hands" that the boy's belt buckle prevented the knife from entering his body.
"It hit the belt, and the knife broke," Trump said, after pulling out an imaginary knife and thrusting it toward the audience.
"Give me a break," Trump fumed. "How stupid are the people of Iowa? How stupid are the people of the country to believe this crap?"
The criticism was a world apart from Trump's restrained demeanor during Tuesday's Republican primary debate, where he issued no attacks on Carson, a retired neurosurgeon who, like Trump, has never held elected office.
But it was a different story Thursday and during an interview with CNN, Trump repeated his accusation that Carson had a "pathological" temper, quoting directly from Carson's book, adding that it equates to the sickness of a child molester.
- 'In the mud' -
Hours later, Trump doubled down on the comparison at the rally in Iowa, where Trump and Carson are running neck-and-neck.
"You don't cure, as an example, a child molester," he told the crowd.
"If you're a child molester, a sick puppy, you're a child molester. There's no cure for that."
Mild-mannered Carson refused to hit back when asked about Trump's tirade.
"It's not the kind of dialogue that I would ever engage in," he told reporters in South Carolina. "That's what's been going on in our country for years that's dragging us in the mud."
Trump followed up his rally rage with a 15-second ad, complete with creepy Friday-the-13th-themed music, continuing the attack on Carson.
"Violent criminal? Or pathological liar? We don't need either as president," the ad says, after a clip of a younger Carson describing the stabbing incident, and then CNN footage of a man questioning Carson's story.
Several rivals took issue with Trump's attack, including Fiorina, who posted a statement to Trump on Facebook saying "you would know something about pathological."
"All the money in the world won't make you as smart as Ben Carson," she wrote.
Trump also directed his ire at extremists in the Middle East, and President Barack Obama's policies there.
"I know more about ISIS than the generals do," Trump boasted, as he crudely summarized his plan to deal with the Islamic State extremist group and take the oil it uses to finance its operations.
"I would bomb the shit out of them," he said to robust applause.
"I would just bomb those suckers. And that's right: I'd blow up the pipes, I'd blow up the refineries. I'd blow up every single inch, there would be nothing left."
Republican candidate Senator Lindsey Graham blasted Trump as "delusional" on Middle East policy and said Thursday's insult fest marked a new low in the Trump campaign.
"I think he melted down last night," Graham told Fox News.