Republican presidential candidate Donald Trump speaks before a crowd of over 3,500 people on Saturday, July 11, 2015, in Phoenix. AP Real-estate developer Donald Trump is furious at Sen. John McCain (R-Arizona) for dismissing the supporters of his presidential campaign.

McCain, the Republican Party's 2008 presidential nominee, was quoted in a Thursday article in The New Yorker criticizing Trump's heated rhetoric against illegal immigration.

The senator also said Trump's big rally last weekend in Phoenix, Arizona, was supported by the "crazies" in his state.

"This performance with our friend out in Phoenix is very hurtful to me," McCain said. "Because what he did was he fired up the crazies."

Trump responded on Twitter by blasting McCain and demanding an apology:

McCain's office declined to comment to Business Insider on Trump's attack.

However one of McCain's top allies blasted Trump in response. Mark Salter, McCain's former chief of staff and coauthor, wrote the following on Facebook, according to a tipster:

Donald Trump isn't just an embarrassment to the Republican Party, or to whatever percentage of unserious self-identified Republicans say they would vote for him. He's an embarrassment to the country. He possesses all the traits snobbish foreigners deride Americans for. He's bumptious, narcissistic, obtuse and full of it. You'd think he was a Brit actor playing an American on the BBC. GOP presidential candidates who can't find the nerve to criticize the guy ought to grow a pair. You'll have done America a good turn, and you'll feel better about yourself.

Updated (7:54 p.m.): With Salter's reaction.