Media playback is unsupported on your device Media caption Dr Ben Carson has endorsed Donald Trump - but what did the rivals say about each other four months ago?

Former Republican hopeful Ben Carson has confirmed his support for his former rival and front-runner Donald Trump in the US presidential race.

He made the endorsement at a joint news conference in Florida with Mr Trump, ahead of primaries there on Tuesday.

The winner of the Republican nomination will face Hillary Clinton or Bernie Sanders for the Democrats, in November.

Mr Carson is the second former candidate to endorse Mr Trump after New Jersey Governor Chris Christie.

A retired neurosurgeon, Mr Carson was an early favourite but dropped out last week after failing to gain significant popular support.

Media playback is unsupported on your device Media caption Footage shows a Trump supporter punching a protester at a Trump rally

The endorsement came a day after an elderly white man was charged with assault for allegedly punching a young protester during a rally for Mr Trump in North Carolina on Wednesday.

Video footage taken by bystanders shows John McGraw, 78, apparently hitting 26-year-old Rakeem Jones as he was being escorted away by police.

Analysis: Anthony Zurcher, BBC News, Miami

There are two sure-fire ways to draw Donald Trump's ire. The first is to directly criticise the New Yorker. The second is to pose a threat to his success.

Ben Carson never did the former but for a few weeks last autumn he challenged Mr Trump in Iowa polls and was rewarded with a full dose of the real estate mogul's derision.

Bygones, however, seem to be bygones. Now the retired neurosurgeon is endorsing the man who once compared him to a child molester.

A Trump-Carson alliance should not come as much of a surprise, however. Both candidates tapped into the desire among disenchanted conservative voters to find a candidate outside the traditional political world. Both offered sharp critiques of the Republican "establishment".

Mr Carson still has a loyal following, particularly among evangelical voters, and he could be a valuable asset to Mr Trump on the campaign trail as the New Yorker looks to secure the Republican nomination in the weeks ahead.

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'Political stuff'

Mr Carson said Mr Trump had a "cerebral" side.

"I have found in talking with him, that there's a lot more alignment, philosophically and spiritually, than I ever thought that there was," Mr Carson said of his former rival.

"Donald Trump talks a lot about making America great. It's not just talk, he means it."

Asked about insults that the two candidates had thrown at each other in the early stages of the campaign, Mr Carson said they had "buried the hatchet".

"That was political stuff," he said. "That happens in American politics."

Media playback is unsupported on your device Media caption Using Hungry Hippos to explain a contested convention

Meanwhile Mr Trump explained why he had targeted his competitor.

"The one person who just kept sneaking up on me, I could not lose him, is Dr Ben Carson," Mr Trump said. "I fought back, and I hit him hard, which is politics, and he understands that."

Mr Carson's endorsement follows a debate in Miami on Thursday night between Mr Trump and his remaining rivals Ted Cruz, Marco Rubio and John Kasich.

Mr Trump, a billionaire businessman from New York with no political experience, has dominated the state primary contests so far.

More contests next Tuesday in five states, including Florida and Ohio, could extend Mr Trump's lead and determine whether Mr Rubio and Mr Kasich can continue in the race.

On Friday Mr Rubio and his campaign admitted that Ohio Governor Mr Kasich had a better chance of winning in the state than he did.

Mr Rubio's communications director, Alex Conant, told CNN Mr Kasich was "the best bet" to defeat Mr Trump in Ohio, while only Mr Rubio could do so in Florida.

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The next votes

15 March: Florida, Illinois, Missouri, North Carolina, Ohio Primaries

22 March: Arizona Primary, Utah Caucuses, Idaho Caucuses (Democratic)

26 March: Alaska, Hawaii, Washington Caucuses (Democratic)

1 April: North Dakota Caucuses (Republican)

5 April: Wisconsin Primary

9 April: Wyoming Caucuses (Democratic)

19 April: New York Primary