His swift march from fringe curiosity to presidential nominee all but over, Donald Trump was confronting dangerous new challenges as the Republican Party he aspires to lead teetered on civil war and questions emerged about how he will fund his campaign going forward.

Mr Trump’s path to the Republican crown was abruptly cleared of all obstacles when, after being soundly defeated in the Indiana primary, Senator Ted Cruz abandoned his campaign late on Tuesday and Governor John Kasich of Ohio signaled his intention on Wednesday also to drop out.

While the hierarchy of the party called for a rallying of support behind Mr Trump, rebellion simmered both in the rank and file of the party and also among some of its more prominent figures. “If we nominate Trump, we will get destroyed.......and we will deserve it,” Senator Lindsey Graham of South Carolina, who was among the original 17 Republicans runners.

Mark Salter, a strategist for John McCain on his 2008 White House run said he would vote for Hillary Clinton, the likely Democrat nominee, before Mr Trump calling him “unfit for office,” and “temperamentally and morally, a narcissistic bigot”. Social media was littered with once die-hard Republicans setting fire to their Republican voter registration cards protesting Mr Trump.

For many who belonged to the #NeverTrump movement, the day of reckoning is here. He has not been stopped. Can they, many of them lifelong Republican operatives or donors, swallow their distaste for him? Steve Schmidt, who was Mr McCain’s manager, predicted that “a substantial amount of Republican officials who have worked in Republican administrations, especially on issues of defense and national security, will endorse Hillary Clinton.”

10 of the scariest things Donald Trump has ever said

It is the scenario that many had feared, a Trump candidacy threatening to tear the Republican Party, also known as the GOP, apart. “Dearly Beloved, we are gathered here today to mourn the GOP, a once-great political party killed by epidemic of Trump,” said the Daily News front page in New York with a picture of an elephant, the GOP’s mascot, climbing into a coffin.

It is unclear what influence party leaders can have. “Look, we’re here. We’re going to get behind the presumptive nominee,” Reince Priebus, the chairman of the Republican National Committee, attempted before adding weakly: “Something new is probably good for our party.”

Whilst he would benefit from party unity, Mr Trump will not beg for it. “I am confident I can unite much of the party,” he told NBC, before adding: “Those people can go away and maybe come back in eight years after we served two terms. Honestly, there are some people I really don't want.”

One possible golden straw was a statement from Mica Mosbacher, the widow of Howard Mosbacher, who was in the George H. W. Bush cabinet, calling “fellow conservatives to unite and support our new nominee Trump”. Ms Mosbacher had previously been a key member of the Cruz campaign’s finance team.

People who will flee America if Donald Trump wins Show all 8 1 /8 People who will flee America if Donald Trump wins People who will flee America if Donald Trump wins Miley Cyrus 'God’ he thinks he is the f***ing chosen one or some shit! … Honestly f*** this sh*t I am moving if this is my president! I don’t say things I don’t mean!' Jemal Countess/Getty Images People who will flee America if Donald Trump wins Whoopi Goldberg 'I don’t think that’s America. I don’t want it to be America. Maybe it’s time for me to move you know' People who will flee America if Donald Trump wins Samuel L. Jackson 'If that mother**er becomes president, I’m moving my black ass to South Africa' People who will flee America if Donald Trump wins Raven Symone 'My confession for this election is, if any Republican gets nominated, I’m gonna move to Canada with my entire family. Is that bad? I already have my ticket. I literally bought my ticket, I swear' People who will flee America if Donald Trump wins Cher 'If he were to be elected, I'm moving to Jupiter' People who will flee America if Donald Trump wins Neve Campbell 'I’m terrified. It’s really scary. My biggest fear is that Trump will triumph. I cannot believe that he is still in the game ... [I'll] move back to Canada' People who will flee America if Donald Trump wins Jon Stewart 'I would consider getting in a rocket and going to another planet, because clearly this planet’s gone bonkers' People who will flee America if Donald Trump wins Randy Blythe 'He could just be a clown. If he is the president, though, I am leaving America 'till he's gone'

The Trump campaign will be looking for other endorsements in the coming days from Republican stalwarts. Although even that necessity was downplayed by Corey Lewandowski, the campaign manager, on Tuesday night. “Of course, we will welcome endorsements of Trump from anyone who wants to endorse Mr Trump,” he told The Independent. “But we have been endorsed by 10 million voters and that’s what matters.”

Ed Rollins, an iconic figure in the party who was Ronald Reagan's 1984 campaign manager, declared he had joined a super PAC supporting Mr Trump, pledging to help raise money for the billionaire to counter the cash advantage he predicted Ms Clinton would have. “They're licking their chops,“ Mr Rollins says of Ms Clinton's team. ”They think they're going to win this thing.“

Mr Trump meanwhile acknowledged that he may be obliged to start taking more money from outside donors. He has spent about $44 million of his own fortune getting to this point, but a general election campaign could cost upwards of $1 billion. That risks damaging his carefully cultivated image of being a self-funded candidate, however.

“I do love self-funding,“ he said yesterday, but acknowledged there are limits even to his wealth. ”Do I want to sell a couple of buildings? I don't really want to do that,” he added.

The rise of Mr Trump threatened also to scramble the Republican strategy for keeping control of the US Senate in November. The majority leader, Senator Mitch McConnell, had previously indicated that if Mr Trump were the nominee he would not object if senators running for re-election disowned him. Some Republicans seeking re-election to the House of Representatives may also be tempted to do the same.