Image copyright Getty Images

Over the past few weeks, word spread that Republican elders were increasingly anxious at the damage Donald Trump was doing to their party's long-term presidential prospects.

With the New York real estate tycoon's latest pronouncement on closing the US borders to all Muslims, that anxiety has become palpable panic.

Virtually all of Mr Trump's fellow candidates have condemned him, and Republican officials, past and present - from former Vice-President Dick Cheney to Speaker of the House Paul Ryan - have joined the fray.

"As a conservative who truly cares about religious liberty, Donald Trump's bad idea and rhetoric send a shiver down my spine," tweeted Matt Moore, head of the Republican Party in South Carolina, a key early voting state in the presidential primary process.

Behind this barrage of criticism is fear that Mr Trump's controversial statements, which would be campaign killers for more traditional candidates, are solidifying his support among increasingly restive conservatives at the expense of the party's long-term ability to assemble the voting coalitions necessary to win the presidency.

Despite his now long record of bombastic remarks, Mr Trump's competitors have surged and receded, while he has remained solid. And he's done so with a brand of anti-immigration, anti-Muslim rhetoric that is flying in the face of a plan the Republican Party set out nearly four years ago to take back the White House in 2016.

Shortly after Mitt Romney's loss to Barack Obama in November 2012, Republican strategists reviewed the election returns and the growing US ethnic diversity and surmised that they had to broaden their party's appeal.

"By the year 2050 we'll be a majority-minority country and in both 2008 and 2012 President Obama won a combined 80% of the votes of all minority groups," Republican Party head Reince Priebus said, adding that his party "cannot and will not write off any demographic or community or region of this country".

With Mr Trump's latest rhetorical flourish, however, Republicans can likely "write off" the support of Muslim US citizens. And his ongoing diatribes against immigration from Latin America aren't going to win the hearts of Hispanics, either. Even if he doesn't capture the nomination, he's pulled his party to the anti-immigrant, nativist right and forced his fellow candidates to take positions that could be harmful when the general election comes around next November.

In perhaps the greatest irony, Mr Trump is waging his war with the Republican establishment and the US media with tools that the conservative movement fashioned and had previously used with gusto.

During his campaign rallies, he often says 70% of journalists are "really dishonest" - capitalising on the distrust of the mainstream media that has been sown by Republican politicians for decades.

Some of the 2016 contenders

Image caption Clockwise from top left: Donald Trump, Jeb Bush, Ben Carson, Marco Rubio, Bernie Sanders, Hillary Clinton

The early Republican frontrunner is Donald Trump

Few see anyone denying Hillary Clinton the Democratic nomination

the Democratic nomination Florida senator Marco Rubio lost some right-wing fans by backing a bipartisan immigration reform package

lost some right-wing fans by backing a bipartisan immigration reform package Retired neurosurgeon Ben Carson briefly led the race but has fallen back in recent weeks

briefly led the race but has fallen back in recent weeks Former Florida governor Jeb Bush is not doing well in the polls despite his name recognition

is not doing well in the polls despite his name recognition Democratic senator Bernie Sanders is drawing huge crowds at his rallies

Meet all of the 2016 hopefuls

Mr Trump also echoes the traditional conservative condemnations of the federal government in Washington, DC, as a bloated, wasteful institution populated by career politicians who are, intentionally or not, bringing harm to the nation. But he takes those lines and uses them as a blunderbuss against everyone in power, Republicans included.

It's a phenomenon seen on a smaller scale in 2010 and 2012, when numerous establishment-sanctioned Republican Senate candidates were defeated in the primary process by grass-roots-backed candidates who were then skewered by their Democratic counterparts in the general election. That dynamic is now playing out on the presidential stage,

Politicians of all stripes, conservatives and liberals, are corrupted by power, Mr Trump said at a rally in Northern Virginia last Thursday.

"They win their election, and they go to Washington, and they're with their wife or husband, and they say: 'Look at the beautiful columns. I don't want to leave this place, this is so beautiful.' And they let us down."

He went on to demean and dismiss one after another of his Republican opponents. Jeb Bush, John Kasich, Marco Rubio, even also-ran George Pataki and former candidate Rick Perry got swiped.

Image copyright Getty Images Image caption Donald Trump tells a Virginia crowd that Republicans in Washington "let us down"

According to conservative commentator Brian Cates, Mr Trump's remarks reveal that he doesn't want to take over the Republican Party, he wants to burn it to the ground from the inside - and his supporters are just fine with that.

"The people endlessly pushing for Trump, they're not doing it because they want a stronger, more conservative GOP," Cates tweets. "They want to destroy the GOP."

Trump supporters are done with traditional politicians, who they feel have turned their back on their campaign promises to bring a conservative revolution to Washington. "They are venting their anger at a political party that consistently let them down and betrayed them," he writes.

Ask Trump supporters why they stand by their man, however, and you'll get a slightly different story. They're angered by the Republican establishment, but they see Mr Trump not as a protest vehicle, but as a leader who can take charge and do what he says.

Image caption Kristie DelAguila (left) and her daughter, Bella, said they were inspired by Donald Trump's honesty

"He just has a way of inspiring people," says Kristie DelAguila, who attended the Trump rally in Virginia. "I loved how honest he is. He's not afraid to tell us what we need to hear."

More than that, however, they contrast Mr Trump's strength with what they perceive as the weakness in the rest of the Republican field.

"I think we have to have a strong leader who makes a stand," says Barbara Bradford, a Virginia schoolteacher. "He doesn't get pushed around. He's got the strength, the leadership, the courage, the mind, the resources. He's got the guts."

Just last week, it seemed the Republican establishment was trying to make peace with the possibility that Mr Trump could win the nomination. The Washington Post obtained a confidential memo in which a senior party official details how Republicans candidates for Congress could campaign with the brash New Yorker at the top of their party ticket.

"Trump has risen because voters see him as authentic, independent, direct, firm - and believe he can't be bought," the memo explains. "These are the same character traits our candidates should be advancing in 2016."

Mr Trump was reportedly scheduled to headline a New York fundraiser for the Republican Party, as well - to break bread and bring in dollars for the party he seeks to lead. Those plans have since been scuttled, as Republicans scramble to distance themselves from Mr Trump's latest conflagration.

With Mr Trump playing with matches inside the Republican tent, however, there may be no safe place left for the party to go.