Paul Ryan, the Republican speaker of the House of Representatives, has said that he is "not ready" to endorse Donald Trump as his party's presidential nominee.
The 2012 vice-presidential nominee and the highest-ranking Republican in Washington, became the latest senior party figure to air concern at the prospect of the polarising businessman representing the party in the November election.
“I am not there right now. I hope to and want to,” Mr Ryan said in an interview on news channel CNN when asked whether he backed the billionaire.
“I think what a lot of Republicans want to see is that we have a standard bearer that bears our standards.”
Mr Ryan, who has spoken out about Mr Trump’s proposal to introduce a temporary ban on Muslims entering the US and the businessman’s refusal to disavow the support for a former Ku Klux Klan leader, said he hoped the party’s presidential nominee “aspires to be Lincoln and Reaganesque” and was someone who “appeals to a vast majority of Americans.”
“I think conservatives want to know: does he share our values and our principles,” said the Wisconsin politician. “There’s a lot of questions conservatives are going to want answers to.”
A number of elected Republicans are struggling with the inevitability that the New Yorker will carry the party’s hopes after his bombastic campaign of insult, anger and controversial plans have left the party fractured.
Mr Trump's path to the nomination was cleared this week after Texas senator Ted Cruz and Ohio governor John Kasich, his last opponents in a field of 16 rival candidates, withdrew from the race.
The prospect of the brash former reality TV star appearing on the Republican ticket with senators and members of Congress seeking re-election has alarmed party veterans.
The 2008 Republican nominee John McCain, hoping to win his sixth six-year senate term in November, articulated the private concerns of Washington insiders when he said during a private fundraising meeting with donors that Mr Trump’s candidacy may affect re-election battles.
Build a wall
Politicians fear Mr Trump’s description of Mexican immigrants as rapists, criminals and drug dealers and his plan to build a wall along the border with
Mexico
will hurt the party in congressional races in states with large Hispanic communities such as in
Arizona
,
Nevada
and Florida.
"If Donald Trump is at the top of the ticket, here in Arizona, with over 30 per cent of the vote being the Hispanic vote, no doubt that this may be the race of my life," said Mr McCain, who lost the 2008 election to Barack Obama.
Mr McCain (79) has said that he would support whoever becomes the Republican nominee, but this is a step too far for some members given that the nominee will more than likely be Mr Trump (69).
Mr McCain's former aide Mark Salter said he would support Hillary Clinton, the expected Democratic presidential nominee, rather than vote for Mr Trump.
“The GOP is going to nominate for president a guy who reads the National Enquirer and thinks it’s on the level. I’m with her,” tweeted Mr Salter, a former senate chief of staff to Mr McCain and one of his key strategists.
The last two Republicans presidents, George HW Bush and his son George W Bush, have said that they would not support Mr Trump, with their spokesman saying they would not take part in the campaign.
One of Mr Trump’s most vociferous critics in the senate, Nebraska’s Ben Sasse, said that a third-party candidate should stand to stop the businessman or Mrs Clinton becoming president.
He said there were “dumpster fires in my town more popular than these two ‘leaders’.”
“Why shouldn’t America draft an honest leader who will focus on 70 per cent solutions for the next four years? You know . . . an adult?” he wrote on Facebook on Wednesdsay night.
Some Republicans are reluctantly accepting Mr Trump's nomination but are carefully crafting their positions . Senator Kelly Ayotte of New Hampshire has indicated that she would "support" Mr Trump for the party's sake but not "endorse" him.
Others took a more drastic approach to show their disapproval, tearing and burning their voter registration cards and posting photos and videos online.
