WASHINGTON — Internal party turmoil over Donald Trump spilled into public alarm on Wednesday after unprecedented self-inflicted mistakes by the Republican nominee, as some conservatives prepared to do the unthinkable: vote for Democrat Hillary Clinton.

A nightmare 48 hours for the embattled Republican flagbearer -- he deepened his public feud with the parents of a fallen Muslim American soldier, refused to back House Speaker Paul Ryan’s re-election bid and used crass language while accepting a supporter’s Purple Heart as a gift -- has highlighted Republicans’ concerns.

Trump allies openly upbraided their candidate on Wednesday for his inability to stay on message, demanding more self-discipline by the political neophyte.

"He has not made the transition to being the potential president of the United States," former House speaker Newt Gingrich, a loyal Trump defender, told Fox Business Network on Wednesday.

In another interview, he warned that Trump will hand Clinton the election unless he changes tack.

"Trump is helping her to win by proving he is more unacceptable than she is," Gingrich told The Washington Post.

Meanwhile, a Fox News poll showed Clinton with a 10 point lead over Trump, at 49 to 39 per cent. Just a month ago that figure stood at six points, Fox News said.

Trump sought to dispel panic earlier on Wednesday, reassuring voters at a Daytona Beach, Florida rally that his campaign has "never been so well united."

A growing list of Clinton converts suggests otherwise.

Trump ’demagoguery’ undermines America

Prominent tech executive Meg Whitman became the latest high-profile conservative to throw her support behind the former secretary of state, saying in a statement on Wednesday that "Donald Trump’s demagoguery has undermined the fabric of our national character."

Whitman is chief executive of Hewlett Packard Enterprise and used to be CEO of eBay. She spent some $140 million of her own money in an unsuccessful run for California governor in 2010.

Her defection comes amid deep concerns at the top of the Grand Old Party about Trump, after a seemingly never-ending stream of controversies that include the nominee urging Russia to hack into Clinton’s emails.

Republican National Committee chairman Reince Priebus backs Trump, but on Wednesday Priebus was being described as "incredibly upset" that the New York real estate mogul refused to endorse Ryan’s congressional re-election campaign.

Trump’s running mate Mike Pence sought to assuage concerns, but his Wednesday endorsement of Ryan for re-election suggested he and Trump were not on the same page.

"I talked to Donald Trump this morning about my support for Paul Ryan and our longtime friendship," Pence told Fox News. "He strongly encouraged me to endorse Paul Ryan in next Tuesday’s primary and I’m pleased to do it."

Meanwhile, Whitman joins other key Republicans who have announced their backing for Clinton.

Richard Armitage, who served as deputy secretary of state for George W.Bush and deputy secretary of defense under Ronald Reagan, defected in June.

Brent Scowcroft, respected national security advisor to two Republican presidents, endorsed Clinton, as did former Republican senator Larry Pressler of South Dakota, who cited Clinton’s support for stricter gun laws.

Bush Treasury secretary Hank Paulson, a former CEO of Goldman Sachs, announced in a Washington Post column that he will vote for Clinton in the hope she can "do the things necessary to strengthen our economy."

Richard Hanna on Tuesday became the first Republican member of Congress to cross the aisle and publicly back Clinton.

Trump "is unfit to serve our party and cannot lead this country," Hanna wrote in a column for Syracuse.com.— AFP