Trump defended his comments repeatedly over the weekend, but appeared to toning down his rhetoric late Monday.
    "If there was a misunderstanding, I would totally take that back," he said in an evening interview on Fox News Channel's "The O'Reilly Factor." On "CBS Evening News," he said, "I don't know if I made a mistake."
    Critics began piling on Trump immediately after he made his comments on Saturday, and new voices emerged on Monday, from veterans groups, Republican colleagues and President Barack Obama's spokesman, who defended McCain and called on Trump to apologize.
    Paul Rieckhoff, founder of Iraq and Afghanistan Veterans of America, said Monday that Trump's "asinine comments" were "an insult to everyone who has ever worn the uniform — and to all Americans."
    White House Press Secretary Josh Earnest said veterans "are entitled to an apology."
    The Des Moines Register, the largest newspaper in early-voting Iowa, published an editorial Monday night calling on Trump to drop out of the race. "Trump has proven himself not only unfit to hold office, but unfit to stand on the same stage as his Republican opponents," the Register said.
    A candidate reliant on campaign contributions probably would be feeling the pain by now.
    Yet the self-funded Trump can proceed as he wishes. After leveling new criticism against McCain early Monday, saying the senator had made America "less safe" through his votes in Congress, he lashed out at fellow GOP presidential aspirants who have criticized his remarks, calling them "failed politicians."
    Trump said he did not need "to be lectured by any of them."
    "If he were dependent on donors for his campaign, he would find the vast majority of donors would be looking for other candidates at this point," said Fred Malek, who has raised money for Republican presidential hopefuls for four decades.
    Presidential competitors in both parties, and the outside groups supporting them, have already raised about $400 million for the 2016 White House contest, the majority of the money coming from donors who face no limits on their contributions.
    Trump hasn't solicited a dime. Reports filed last week with federal regulators show he loaned his campaign $1.8 million. He has never held a fundraising dinner, and he has never sent email asking for others to chip in $25 — hallmarks of a traditional presidential campaign.
    "I don't need anybody's money. It's nice," Trump proclaimed during his presidential announcement June 16 in New York City. "I'm using my own money. I'm not using the lobbyists. I'm not using donors. I don't care. I'm really rich."
    Trump filed details of his personal wealth with federal regulators last week that declare a net worth in excess of $10 billion.
    "Being a billionaire means you're the master of your own domain," Luntz said.
    He would know: Luntz once worked for Texas businessman H. Ross Perot, perhaps the best-known presidential candidate who paid his own way. In 1992, Perot ran as an independent candidate, using almost $64 million of his fortune to get his name on ballots across the country.
    This year, with Republican Party pressure building, Luntz wonders if Trump will break off and go the Perot third-party route.
    "You may be able to look back on this day as the beginning" of that campaign, he said. "You make up your own rules."
    On the other hand, a self-financed candidate can also be his or her own worst enemy, said Ed Rollins, Perot's onetime campaign manager.
    Rollins predicted Trump would follow the same path as his former boss: off a cliff.
    Perot was polling ahead of the major-party candidates in June before the election but ended up not winning a single state in November.
    "He first promised to spend whatever it took to win, and we presented him with a budget," Rollins said. "He balked at that. He argued over every item. The Ross Perots, the Donald Trumps, they don't want to be told what to do."