With their party in crisis, chairman Reince Priebus appealed to Mr Trump’s adult children to help amid new signs of a campaign in trouble. Mr Trump’s operation has been beset by internal discord, including growing concern about election preparedness and a lack of support from Republican leaders.
One source said Mr Trump privately blames his own staff for failing to stop the backlash from his own party after he criticised an American Muslim family whose son, a US Army captain, was killed in Iraq.
The inner tension comes as Mr Priebus and other high-profile Trump allies consider whether to confront the candidate directly to encourage a new approach following a series of startling statements.
In the middle of the uproar over his continued criticism of the Khan family, Mr Trump infuriated Mr Priebus and other party leaders by refusing to endorse Republican House Speaker Paul Ryan’s re-election.
Mr Trump dismissed suggestions that the frustration was hurting his campaign, even as he openly contemplated losing.
“Wouldn’t that be embarrassing to lose to crooked Hillary Clinton? That would be terrible,” he said during a campaign stop in battleground Florida. He also insisted: “We’ve never been this united.”
“The candidate is in control of his campaign,” campaign chairman Paul Manafort told Fox News Channel, highlighting his inability to control the nominee. “And I’m in control of doing the things that he wants me to do in the campaign.”
“I would say in the last couple of weeks, he has been remarkably under-performing and we’ll see whether or not he can take a deep breath and learn these lessons,” said former house speaker Newt Gingrich.
Mrs Clinton, meanwhile, kept up her assault on Mr Trump’s business practices, holding up a Trump-branded tie as she spoke at the Knotty Tie Company in battleground Colorado.
She told employees in Denver: “I really would like him to explain why he paid Chinese workers to make Trump ties, instead of deciding to make those ties right here in Colorado.”
Mr Trump stunned Republicans by saying on Tuesday that he was not ready to endorse Mr Ryan, who faces a primary contest in Wisconsin next week.
Mr Ryan has backed Mr Trump despite deep differences on policy and temperament, and has encouraged other Republicans to unite behind the party’s nominee.
Vice presidential nominee, Indiana Governor Mike Pence, said he spoke to Mr Trump on Wednesday: “He strongly encouraged me to endorse Paul Ryan in next Tuesday’s primary. And I’m pleased to do it.”