With just under 100 days until the presidential election, tensions between Donald Trump and the Republican Party have reached a boiling point in the wake of his feud with the parents of slain Muslim-American soldier Humayun Khan.

Republican strategists and former elected officials are deeply perplexed by their nominee's self-destructive impulses, his penchant for courting controversy, and his move to further inflame intra-party chaos this week by refusing to endorse House Speaker Paul Ryan or Arizona Senator John McCain for re-election.

Some Republicans have given up on their dreams of a post-primary "pivot" and are ready to concede the White House and instead focus resources on saving their Senate majority as well as candidates down the ballot.

Trump, 70, is "facing an electoral wipeout at this point. I think getting him to change his behavior is a fool's errand," said Matt Mackowiak, a Texas-based Republican strategist. "He's now doing intentional damage to the party. He's hurting our candidates. It's clear he doesn't care about the Republican Party, so what responsibility does the Republican Party have to him at this point?"

It has been a rough week for Trump. Polls show that the Democratic national convention erased Trump's lead after the Republican gathering and gave Democratic nominee Hillary Clinton back her advantage. He's alienated prominent Republicans such as former representative Vin Weber, who told CNBC's John Harwood he'll probably leave the party if Trump wins. The Trump-Khan spat was the final straw for several GOP figures who came out for Clinton-including former California gubernatorial nominee Meg Whitman, former Jeb Bush adviser Sally Bradshaw, former Chris Christie adviser Maria Comella, and retiring Rep. Richard Hanna.

"It's a stupid fight to pick," said Tom Davis, a Republican former representative from Virginia, who said he isn't ready to get behind Trump's campaign. "The rhetoric he used was bad," he said, adding that Trump was hurting himself by "not running a disciplined campaign."

"I wince some nights when I watch Trump just blowing opportunities to score points and going on defense when he ought to be on offense," Davis said. "It's just not the kind of campaign you'd be enthused about."

In a further sign of discord, Trump's running mate, Mike Pence, on Wednesday endorsed Ryan for re-election in Wisconsin, even as the presidential nominee refused. News swirled that Republican National Committee Chair Reince Priebus, a fellow Wisconsinite who is close to Ryan, was livid about Trump's snub.

"There's a conflict within the Trump campaign," top Trump aide Paul Manafort acknowledged Thursday on ABC News.

Manafort's comment came a day after he went on Fox News and dismissed reports about internal chaos among Trump aides, which has overshadowed what the Trump campaign says was a remarkable $80 million fundraising haul in July. "The turmoil-this is another Clinton narrative that is put out there and the media is picking up on," he said, arguing that "the campaign is in very good shape-we are organized, we are moving forward."

Trump senior adviser Kellyanne Conway rejected notions of Trump dropping out of the race as "wishful thinking."

But the reports of a campaign in disarray have pro-Trump Republicans worried.

"I'm mostly concerned with the rumors coming out that Manafort has no operational control and that Trump is winging it. If they're not a campaign at the top this could be really bad for Republicans all the way down the ticket," said John Feehery, a Republican strategist and lobbyist. "All this other stuff is kind of typical-his blather and his inability to restrain his emotions. I don't see mass defections from his voters on this."

Still, Trump's rough stretch doesn't mean GOP politicians will reject him, at least for the foreseeable future. His command of an energized plurality of the party base during the primaries means Republicans up and down the ballot this fall will rely on his voters to win their races.

"If you're an elected official you have to appeal to them somehow. Just walking away from Trump is political suicide," Feehery said. "In most Republican districts, Trump is very popular. And all this politically incorrect stuff is very popular with the Republican base. ... You can't diss the Donald Trump voter."

Trump rallied his base Wednesday at a campaign stop in Daytona Beach, Florida, by labeling the U.S. a "third-world nation" and taking aim at President Barack Obama and Clinton. "We've got to stop being the stupid country run by very stupid people," he said. "She'll be worse than Obama. Believe me."

In a sign that Trump's refusal to endorse Ryan or McCain is about settling personal scores, the nominee encouraged his Florida crowd to vote for former 2016 rival Marco Rubio's re-election bid to the Senate. "I endorsed Marco Rubio, he endorsed me. He's doing well. Go for Marco," Trump said. Unlike Ryan or McCain, who released statements rebuking Trump's remarks on Sunday insulting the parents of Capt. Khan, Rubio largely steered clear of the controversy.

Trump's actions in recent days have earned an admonishment from Newt Gingrich, a former House speaker and one of his most loyal supporters. Wednesday on Fox News, Gingrich said Trump must "slow down, take a deep breath, and reorganize how he's operating so he gets to the standard of the potential president of the United States."

"He has not done that up 'til now. It's been significantly to his disadvantage," Gingrich said. "So I think some of what Trump has done is very self-destructive. ... I don't know if it's a fixable problem but I think it's a very big moment for Trump. He has got to find a way to slow down, really learn some new lessons. This is like The Apprentice except he's the apprentice and not the boss. He doesn't get to say, 'You're fired.' The American people get to say, 'You're fired.'"