Several US presidential contenders have voiced anti-Islam or anti-immigration concerns during the campaign.

Washington, United States – Most of the media coverage of the US presidential campaign has been swallowed by Donald Trump over the past 24 hours, after he called for a complete ban on all Muslims entering the US.

The latest incendiary comments from the Republican front-runner on Monday stood out because of the outrage they provoked, not just among Democrats but also among his fellow Republicans.

Former Florida Governor Jeb Bush called Trump “unhinged”. In one of the strongest attacks, Senator Lindsey Graham told Trump to “get the hell” out of his party.

The Republican speaker of the US House of Representatives, Paul Ryan, said that Trump’s comments were not what his party stood for.

Yet what Donald Trump has been expressing is at the extreme end of a theme which has been visited by numerous Republican candidates over the past few months.

In September, Dr Ben Carson, the neurosurgeon chasing the nomination, said there could not be a Muslim president of the US saying any candidate would have to “reject the tenets of Islam”.

The reaction at the time, calling his comments unconstitutional and un-American, have clearly left an impression.

Confronted with Trump’s latest outburst, he said: “That’s not who were are. We do not discriminate on people based on religion. That’s unconstitutional, that’s in the First Amendment, so we would never want to do that.”

New Jersey Governor Chris Christie said what Donald Trump was proposing was not the way to keep America safe.

Yet in the aftermath of the ISIL attacks in Paris, he called for an urgent reassessment of the programme that allowed Syrian refugees into the country, saying he wouldn’t even admit “a five-year-old orphan”.

Marco Rubio, the Florida senator and one of the Republican frontrunners, claimed Trump’s comments were “not well thought out. It was impulsive”.

Yet in November, when Trump advocated a crackdown on Muslims, Rubio went further. He suggested shutting down cafes or shops or restaurants, in fact “any place where radicals are being inspired”. He even equated Muslims with Nazis.

Senator Rand Paul from Kentucky, who consistently polls in single figures, criticised Trump strongly. He said it would be a “mistake to base immigration or moratoriums based on religion”.

Yet, he immediately added: “I’ve called for something similar.” Indeed, he proposed a measure suspending visas to refugees from around 30 countries which have “large jihadist movements”.

Ted Cruz, the Texas senator, voted for that failed amendment. He actually drafted a bill to ban refugees from countries with territory controlled by a “terrorist” group, while making an exception for Christians. Just last month, he explained: “There is no meaningful risk of Christians committing acts of terror.”

And he has pointedly refused to criticise Donald Trump, believing that if his campaign derails, the supporters will move easily across to him.

One Republican in Iowa, the state where the first nomination contest takes place early next year, suggested that Cruz was in fact “a toned-down” Donald Trump.

Among Trump’s strongest critics has been Jeb Bush. The former Florida governor insists Trump will not get the Republican nomination. He’s even gone as far to suggest he’s a plant for the Clinton campaign. Back in November, he warned about scapegoating Muslims, but also said that Christian refugees should be given a priority coming into America.

Ohio Governor John Kasich has said he may not support Donald Trump if he becomes the official Republican nominee.

At the time of writing, he’s the only candidate to do so.

In November, a political action committee which supports Kasich started airing a TV ad which directly criticises Trump.

Paraphrasing the famous words of late German pastor and concentration camp survivor Martin Niemoller, the ad says:

“You might not care if Donald Trump says Muslims must register with their government because you’re not one. And you might not care if Donald Trump says he’s going to round up all the Hispanic immigrants, because you’re not one. And you might not care if Donald Trump says it’s OK to rough up black protesters, because you’re not one. And you might not care if Donald Trump wants to suppress journalists, because you’re not one…But think about this: if he keeps going and he actually becomes president, he might just get around to you. And you better hope there’s someone left to help you.”

John Kasich is currently polling at just 7 percent.