WASHINGTON • Republican presidential hopeful Donald Trump has launched new attacks on immigrants, telling supporters that Somalis and other refugees from "terrorist nations" should be barred from entering the United States.
His broadside on Thursday came as a raft of the latest national and battleground polls found him slipping well behind Mrs Hillary Clinton, one week after the end of the Democratic convention - with the Republican candidate still reeling from a public feud with the parents of a slain Muslim American war hero.
Mr Trump, who has built his campaign around an anti-immigration platform, speaking at a rally in Portland, Maine, said: "We are letting people come in from terrorist nations that shouldn't be allowed because you can't vet them. You have no idea who they are. This could be the great Trojan horse of all time."
The comments echoed his earlier warnings about how terrorists, including Islamic State in Iraq and Syria members, will sneak into the US as refugees.
Mr Trump singled out the Somali immigrant population as an example of the "thousands" of refugees who have come to Maine and other US states and caused problems.
He said efforts to resettle Somali refugees - many of them in Minnesota - were "having the unintended consequence of creating an enclave of immigrants with high unemployment that is stressing the state's safety net as well as creating a rich pool of potential recruiting targets for Islamist terror groups".
He then listed several immigrant groups - from Afghanistan, Iraq, Morocco, Pakistan, the Philippines, Somalia, Syria, Uzbekistan and Yemen - who were arrested for conducting or threatening to carry out violent attacks, teaching bomb-making to recruits, and otherwise supporting terror groups. "We're dealing with animals," he said.
Mr Trump caused an uproar in December last year when he called for a temporary ban on all Muslims entering the US. He has also harangued his Democratic rival, Mrs Clinton, for wanting to allow many more refugees into the country than President Barack Obama has.
"Hillary Clinton wants to have them come in by the hundreds of thousands," Mr Trump said on Thursday, to a chorus of boos.
"You're going to have problems like you've never seen," he added.
Meanwhile, new polls are signalling trouble for Mr Trump. "There has clearly been a significant movement towards Clinton in the last week," said Mr Ken Goldstein, a professor of politics at the University of San Francisco and polling analyst for Bloomberg Politics. "Some of it is a Clinton post-convention bounce, but more of it seems to be a Trump deflation or implosion."
A new poll in Pennsylvania, which is seen by Mr Trump's top strategists as a crucial bellwether state, finds him trailing Mrs Clinton by 11 percentage points among likely voters surveyed by Franklin & Marshall College.
Nicknamed the Keystone State, the electoral vote-rich state that 2012 Republican nominee Mitt Romney lost by just 5 points is arguably a must-win battleground for Mr Trump, due to demographics that are uniquely suited to his appeal.
For instance, it is 20 per cent whiter than the US as a whole, and has a large working-class base that is reeling from the loss of manufacturing jobs and sympathetic to Mr Trump's anti-trade views. Other battleground state polls of likely voters show similar trends. In Michigan, another Democratic-leaning Rust Belt state that Mr Trump is targeting, he trails Mrs Clinton by nine percentage points in a survey done by Detroit News and WDIV-TV.
In Florida, an electorally rich and closely divided state, he trails her by six percentage points in a Suffolk University poll.
In New Hampshire, a purple state that was the site of Mr Trump's first blow-out victory in the Republican primary, he is down by a whopping 15 percentage points against Mrs Clinton, according to a WBUR poll.
Nationally, the picture is not much better for him. A McClatchy/Marist national poll found him down 15 points among registered voters - up from his three-point deficit last month.
That is a bigger gap than any seen by Mr Romney in the polls during his 2012 campaign and recorded by RealClearPolitics, which closely tracks presidential election surveys.
Facing urgent calls to stabilise his candidacy and declining poll numbers, Mr Trump struggled to refocus his message after threatening to withhold his endorsement from top Republican officeholders, including House Speaker Paul Ryan.
Hampering Mr Trump's efforts to move past the controversy, he and his running mate, Indiana Governor Mike Pence, broke ranks for the second time in two days on questions of party unity.
Having split with Mr Trump over his refusal to endorse Mr Ryan, Mr Pence went his own way again on Thursday, telling a TV station in Norfolk, Virginia that he supported Mr John McCain of Arizona and Ms Kelly Ayotte of New Hampshire - two senators running for re-election whom Mr Trump has snubbed.
AGENCE FRANCE-PRESSE, BLOOMBERG, NEW YORK TIMES