Republican U.S. presidential candidate businessman Donald Trump (L) listens as rival candidate Dr. Ben Carson speaks during the debate held by Fox Business Network for the top 2016 U.S. Republican presidential candidates in Milwaukee, Wisconsin, November 10, 2015. REUTERS/Darren Hauck

(Reuters) – Republican presidential candidate Ben Carson shrugged off an angry rant from rival Donald Trump on Friday after the bombastic billionaire tested the patience of the party’s base by saying Carson had pathological tendencies similar to a child molester.

The fallout from Trump’s nasty broadside reverberated in Orlando where Trump and Carson, the two front-runners, were among a host of candidates speaking at the Florida Republican Party’s Sunshine Summit.

“I expect that kind of thing,” Carson said in Greenville, S.C., when asked about Trump’s comments. “That’s what’s been going on in our country for years… and I don’t expect it to change any time soon but I don’t have to get into it.”

The day-long speechfest also put on display the increasing tensions between two up-and-coming challengers for the 2016 Republican presidential nomination, Senators Marco Rubio and Ted Cruz, who clashed on Thursday over immigration.

Cruz, of Texas, had blasted Rubio, of Florida, as favoring amnesty for illegal immigrants by sponsoring a 2013 legislative effort in the Senate.

Speaking to reporters in Orlando, Rubio said Cruz had supported a legal pathway to citizenship for illegal immigrants and promoted an amendment to that effect, and now claims he did not.

“He bragged about how his amendment would bring people out of the shadows,” Rubio said. “He’s changed his position. He has a right to change his position.”Rubio and Cruz were among the candidates appearing in Orlando, along with three other candidates: Former Florida Governor Jeb Bush, South Carolina Senator Lindsey Graham and former Arkansas Governor Mike Huckabee.

Trump, frustrated that Carson has stolen the lead from him in polls of Iowa Republicans, launched a diatribe against the retired neurosurgeon at a rally in Fort Dodge, Iowa, on Thursday night. Iowa will hold the first nominating contest on Feb. 1 on the road to the November 2016 election.

Trump said Carson has a “pathological” temper, alluding to compulsive behavior similar to that of a child molester.

“If you’re pathological, there’s no cure for that,” Trump said. “If you’re a child molester, there’s no cure. They can’t stop you.”

At one point, Trump flipped his belt buckle over to try to cast doubt on a frequently cited anecdote from Carson, that he tried to stab someone as a child but the person’s belt buckle prevented injury. Carson says the incident helped turn him to the Christian faith.

“Give me a break,” Trump said. “How stupid are the people of Iowa? How stupid are the people of the country to believe that crap?”

While Trump has made a number of outlandish statements with no penalty from Republican voters, turning on Carson in such a bitter way could mark a turning point for the New York mogul whose take-charge attitude has kept him at the top of the polls for months.

Trump kept up the attention on Carson’s past with an Instagram video showing TV footage of Carson talking about the knife incident. Words on the screen say: “Violent criminal? Or pathological liar? We don’t need either as president.”

Carson refused to respond in kind, in keeping with his generally laid-back manner.

“It’s up to the people of Iowa and they will decide if they want to listen to the usual politics…or if they want to do something different,” he said.

Rubio, asked about Trump’s comments about Iowa, said Iowa voters are “some of the nicest” people in the country. Another Republican candidate, Carly Fiorina, sounded off on Facebook about Trump’s comments early on Friday.

“Anyone can turn a multi-million dollar inheritance into more money, but all the money in the world won’t make you as smart as Ben Carson,” she said.