WASHINGTON (Reuters) - U.S. presidential candidate Ben Carson recommended praying for rival Donald Trump after the real-estate mogul and television personality, in a 95-minute rant in Iowa, likened him to a child molester, Carson's business manager said on Friday.

"When I spoke with Dr. Carson about this yesterday how we should respond, you know he was so sad about it. He said: "Pray for him." He feels sorry for him because he really likes Mr. Trump," Armstrong Williams, who often acts as Carson's surrogate in the media, told CNN.

"To see him just imploding before our very eyes - it's just sad to watch," Williams said.

Speaking in Iowa on Thursday evening, Trump, a leading contender for the Republican nomination in the 2016 presidential election, cast doubt on Carson's oft-reported story of lunging at someone with a hunting knife as a child, an episode Carson says led him to his Christian faith.

A retired neurosurgeon, Carson has emerged as the main challenger to Trump's top position in national polls and popularity in early deciding states. A Reuters/Ipsos poll this month found 31 percent of Republicans favored Trump. Carson followed at 18 percent.

"Give me a break," Trump said in his Thursday speech, where he also lashed out at other Republican candidates and Democratic front-runner Hillary Clinton. "How stupid are the people of Iowa? How stupid are the people of the country to believe that crap?"

He said the incident showed Carson had a "pathological" temper.

"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."

Carson has said his intended stabbing victim's belt buckle blocked his knife, a detail Trump singled out in his rant.

"Lo and behold! It hit the belt. It hit the belt and the knife broke," Trump said mockingly.

Other Republican candidates came to Carson's defense early Friday and slammed Trump for his controversial plans on foreign policy and immigration.

"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," candidate Carly Fiorina wrote on Facebook.

Republican candidate Lindsey Graham called Carson a "good, decent man," and said of Trump: "I think he melted down last night."

"He has no clue what he's talking about," Graham, a South Carolina senator, said on Fox News. "Over time, that will take a toll - I hope."

(Reporting by Lisa Lambert; Additional reporting by Megan Cassella; Editing by Bernadette Baum)