Former Republican rival Ben Carson backs Donald Trump for White House bid

Former rival Ben Carson has backed Republican presidential frontrunner Donald Trump, becoming the second former presidential candidate to support the billionaire businessman in the race for the White House.

Carson, a retired neurosurgeon who dropped out of the race on March 4, follows New Jersey governor Chris Christie, a former candidate who also backed Trump after earlier dropping out of the race for the party’s nomination ahead of the November 8 presidential election. Carson made the announcement at a joint news conference with Trump in Florida, ahead of that state’s primary on Tuesday.

Trump and his Republican rivals turned their Florida presidential debate into a mostly respectful, but still pointed, discussion of Islam and trade.

Mr Trump shook his head and declared to the Miami audience at one point: “I can’t believe how civil it’s been up here.”

Ted Cruz and Marco Rubio did not hesitate to lay out their differences with Mr Trump, but the candidates largely managed to present those arguments without vitriol.

In a lengthy discussion of the threat posed by radicalised Muslims, Mr Trump refused to back away from his recent statement that “Islam hates the West”, saying he would not stoop to being “politically correct” by avoiding such statements.

Mr Rubio hit back, saying: “I’m not interested in being politically correct. I’m interested in being correct.”

The Florida senator noted the Muslims in the US military and buried in Arlington National Cemetery and said the only way to solve the problem of violent extremists was to work with Muslims who were not radicals.

Mr Cruz bundled together his criticisms of Mr Trump for what he called simplistic solutions on trade and on Islamic terrorists, saying: “The answer is not to simply yell, ‘China: bad, Muslim: bad’.”

Mr Trump, though, clearly was intent on projecting a less bombastic and more presidential image.

His closing message was: “Be smart and unify.”

“We’re all in this together,” he said early on, sounding more like a conciliator than a provocateur as he strives to unify the party behind his candidacy.

“We’re going to come up with solutions. We’re going to find the answer to things.”

His rivals, in a desperate scramble to halt his march to the nomination, gradually ramped up their criticism as the night wore on.