Donald Trump has insisted there is "great unity in my campaign" - although there are several indications that the Republican Party is turning against its nominee.
Senior Republican figures are growing increasingly concerned about Mr Trump's behaviour following his criticism of the family of a dead Muslim American soldier and his refusal to back the re-election campaign of Paul Ryan, the house speaker.
Frustration at Mr Trump's divisive tactics and insulting comments reached new heights on Wednesday, with several extraordinary developments.
Senior Republicans, including Reince Priebus, chairman of the GOP, Rudy Giuliani, former New York City mayor, and Newt Gingrich, the former house speaker, were reportedly considering an "intervention" meeting with Mr Trump.
They hoped to talk Mr Trump into "a dramatic reset of his campaign", NBC reported.
"A new level of panic hit the street," Scott Reed, chief strategist for the US Chamber of Commerce, told the 'Washington Post'. "It's time for a serious reset."
Mr Gingrich, a Trump ally, said his friend currently stood no chance of beating Hillary Clinton in November.
"The current race is 'which of these two is the more unacceptable', because right now neither of them is acceptable," Mr Gingrich said.
"Trump is helping her to win by proving he is more unacceptable than she is."
Mr Priebus was said to be "livid" over Mr Trump's behaviour and appealed to the New York billionaire's adult children to help calm the situation.
A Republican source told Reuters that Mr Priebus "feels like a fool".
More than any other senior figure in the Republican establishment, Mr Priebus worked to bring Mr Trump into the party's fold despite the New York businessman's status as an outsider.
According to AP, Mr Priebus has already spoken to Trump campaign chairman Paul Manafort and to the Trump children, who are believed to agree that the nominee needs to stop picking fights within his own party and to take a step back from his criticism over the past few days of the Khans, the parents of Muslim American veteran Captain Humayun Khan.
Mike Pence, the Republican vice presidential candidate, openly split with Mr Trump by giving his endorsement to Mr Ryan.
In an indication of how deep the divisions are - even within the Trump campaign itself - Mr Pence said: "I talked to Donald Trump this morning about my support for Paul Ryan, our longtime friendship. He strongly encouraged me to endorse Paul Ryan in next Tuesday's primary. And I'm pleased to do it."
Mr Trump antagonised the higher echelons of the Republican establishment on Tuesday when he said he was "just not quite there yet" when it came to backing Mr Ryan.
He also refused to endorse John McCain in his re-election bid on Tuesday. Both had been critical of his attacks on the Khan family.
There were reports that some Republicans were exploring what the process would be should Mr Trump himself pull out of the race.
ABC reported that if Mr Trump pulled out before early September, it would be up to the 168 members of the Republican National Committee to choose a successor.
In this scenario, there would be enough time get the next nominee's name on the ballot in enough states to win in November's general election.
However, there are no indications at this stage that Mr Trump wants to step aside.
Kellyanne Conway, a spokeswoman for the Trump campaign, reportedly said: "I would push back on any formal report that the candidate is going to leave the race."
Despite the animosity within the party, Mr Trump was remorseless, taking to Twitter to state: "There is great unity in my campaign, perhaps greater than ever before."
Mr Manafort also attempted to give the impression that there was no panic within the Trump camp, telling Fox News: "The candidate is in control of his campaign. And I'm in control of doing the things that he wants me to do in the campaign."
"The only need we have for an intervention is maybe with some media types who keep saying things that aren't true."
Republicans' frustration with Donald Trump has reached new heights, with party leaders scrambling to persuade him to abandon divisive tactics that have triggered sinking poll numbers and low morale.
Mr Priebus is appealing to the New York billionaire's adult children to help amid new signs of a campaign in trouble.
Trump's operation has been beset by internal discord, including growing concern about general election preparedness and a lack of support from Republican leaders, according to two people familiar with the organisation's inner workings.
One of the sources said that Trump privately blames his own staff for failing to quiet the backlash over his Khan family outburst.
Meanwhile, Clint Eastwood has said he would vote for Donald Trump over Hillary Clinton, claiming the Republican "is on to something".
The legendary actor and director stopped short of fully endorsing Mr Trump for president, but praised him for "saying what's on his mind".
Eastwood, who served as the Republican mayor of Carmel in the 1980s, did, however, add in an interview with 'Esquire' magazine that Mr Trump had said "a lot of dumb things". (© Daily Telegraph London)