Former US vice presidential candidate and reality TV star Sarah Palin has given her backing to Republican frontrunner Donald Trump. 

The former governor of Alaska on Tuesday told supporters gathered at a rally in the US state of Iowa that Trump would "kick ISIS ass", referring to the Islamic State of Iraq and the Levant group.

"He is from the private sector, not a politician," Palin said in an animated speech after joining the business mogul and former host of TV's The Apprentice onstage, later asking the audience if she could "get a hallelujah." 

Palin was running mate to US senator John McCain during his unsuccessful bid for the presidency in the 2008 election, which was won by current President Barack Obama.

She said there was nothing wrong with Trump being a multibillionaire and that it did not make him an elitist, citing all the time he had spent with construction workers as a real-estate developer.

As Trump stood alongside, Palin said: "The status quo has got to go," adding the political establishment had been "wearing political correctness kind of like a suicide vest", the Reuters news agency reported.

'Greatly honoured'

In a statement before the event, Trump said he was "greatly honoured" by the endorsement. "She is a friend, and a high-quality person whom I have great respect for."

Trump has led national opinion polls among Republicans for months but is in a tight contest with Ted Cruz, a Canadian-born senator for Texas, for the support of Iowa Republicans, who lean conservative and whose evangelical Christians comprise a major voting bloc.

Palin, who often discusses her Christian faith, is popular among that group and endorsed Cruz when he ran for the US Senate in 2012.

Cruz responded to her switch of allegiance with magnanimity.

"Regardless of what she does in 2016," he tweeted, "I will always be a big fan."

What does Palin's backing mean for Trump and the US?

Source: Reuters