WASHINGTON, Aug. 3 (Xinhua) — Republican presidential nominee Donald Trump, facing growing frustration and division among the Republican elite and donors, claimed Wednesday that his campaign has never been in better shape and his party has never been so well united.

"The campaign is doing really well. It's never been so well united. It's the best in terms of being united since we began," Trump announced at a rally in Daytona Beach, Florida.

"I think we have never been this united," Trump went on, despite the public view that he has been trapped in a political meltdown created largely by himself.

The New York billionaire made the remarks after being sharply criticized by Republican leaders for his feud with the parents of a Muslim-American soldier killed in Iraq War and his reluctance to endorse either Republican House Speaker Paul Ryan or Arizona Senator John McCain in their re-election bid. He even praised Ryan's primary challenger Paul Nehlen on Twitter.

Both Ryan and McCain have endorsed Trump, though they keep obvious distance and often express their disagreements with the party's wild-card candidate.

Earlier on Wednesday, even Trump's running mate Mike Pence publicly contradicted him by announcing strong support for Ryan.

"I strongly support Paul Ryan, endorse his re-election. He is a longtime friend, a strong conservative leader," Pence told Fox News.

Trump was also rebuked by his core allies, including former House Speaker Newt Gingrich and New Jersey Governor Chris Christie, over his reckless attacks on the slain Muslim-American soldier's parents.

"The question is can he in August slow down, take a deep breath and reorganize how he's operating so that he can get to the standard of running for president," Gingrich told the CNBC on Wednesday, noting that Trump has been "self-destructive."

"I think he has the potential to win the election, I think he has potential to be a historic president, but to do that he's got to grow into the size of the job," said Gingrich.

Ari Fleischer, a former White House spokesman, expressed another sense of bewilderment among Republicans when he reflected on Trump's take-no-prisoners political style.

"He is such a good counter puncher that he is knocking himself out," Fleischer said Wednesday on CNN, "If he would focus on Hillary, if he'd focus on the economy, if he'd talk (President Barack) Obama and we don't want a third term, he could win this race. He's hurting himself and hurting the cause."

Amid continuous controversy, several high-profile Republican donors, including billionaire businesswoman Meg Whitman, openly turned their back against Trump and said they would not vote for the Republican candidate in November.

Earlier this week, Stanley Hubbard, a Minnesota broadcasting billionaire and a major donor of the Republican Party, wrote a letter urging Trump to "start saying things that are sensible; have some sensitivity," according to a report of The Hill.

It is expected that Trump has to heavily rely on the Republican Party for fundraising since he lacks the political infrastructure of a conventional political candidate. Through the network with the Republican National Committee, the Trump campaign collected 80 million dollars in fundraising in July.