Donald Trump called, Monday, for a total ban on Muslims entering the United States, a stunning policy proposal with a chilling echo of the identity-based border controls abandoned by the country generations ago.
"Trump is calling for a total and complete shutdown of Muslims entering the United States until our country's representatives can figure out what is going on," said the statement.
"Where this (jihadist) hatred comes from and why we will have to determine. Until we are able to determine and understand this problem and the dangerous threat it poses, our country cannot be the victims of horrendous attacks by people that believe only in jihad, and have no sense of reason or respect for human life."
It was unclear how broadly Trump would apply such a policy, had he the power to do so. A Trump spokeswoman, asked whether the ban would extend to other travellers, such as tourists and Muslim Americans returning from work or study abroad, was quoted in various media reports as saying: "Everyone."
The announcement provoked expressions of shock from some of Trump's Republican rivals, although the strongest ones came from also-ran candidates — not from his closest rivals Ben Carson, Ted Cruz and Marco Rubio, who have been far more hesitant to attack Trump and potentially antagonize his supporters.
Jeb Bush, who has dropped well back in the race, was more direct.
"Donald Trump is unhinged," Bush tweeted. "His 'policy' proposals are not serious."
New Jersey Gov. Chris Christie called it the kind of thing people say when they "have no experience and don't know what they're talking about." Sen. Lindsey Graham said Trump was risking the lives of American allies, interpreters, diplomats and troops with his bigoted comments.
One immigration lawyer called the idea a throwback to a dark past. Trump's statement came seven decades after the United States began repealing laws designed to exclude Asians.
"(This) may remind some of similar attempts by the United States to exclude specific groups, in an attempt to alter the ethnic composition incoming immigration," said Henry Chang, a Canadian lawyer with Blaney McMurtry and an expert on U.S. immigration law.
"These prior laws were considered some of the most racist laws in the history of United States immigration."
He said the most significant exclusion law ever enacted by the U.S. was the Chinese Exclusion Act of 1882, and he cited other laws between 1917 and 1924 that were repealed over subsequent decades.
Trump's stated rationale for the new policy: polls that, he says, suggest a sizable minority of Muslims support global jihadism. Some critics questioned the methodology of the polling to which he appeared to be referring.
It was a sharp contrast to the message a day earlier from President Barack Obama. The president used a prime-time address to warn against discrimination. He called the Islamic State of Iraq and the Levant a death cult of thugs and killers who do not represent Muslims.
"If we're to succeed in defeating terrorism, we must enlist Muslim communities as some of our strongest allies, rather than push them away through suspicion and hate," Obama said.
"Just as it is the responsibility of Muslims around the world to root out misguided ideas that lead to radicalization, it is the responsibility of all Americans, of every faith, to reject discrimination. It is our responsibility to reject religious tests on who we admit into this country."
Members of the Republican establishment have publicly lamented Trump's effect on the party's primary process, with statements about Latinos and Muslims that other candidates have sometimes shied away from criticizing.
Conservative commentator Bill Kristol tweeted Monday: "(It's) important to save conservatism from him," he said. "Good news: Trump's statement reeks of desperation. He knows he won't be nominee.
"Bad news: The statement itself is bad for the country."