AP
Republican presidential candidate Donald Trump speaks before a crowd of over 3,500 Saturday, July 11, 2015, in Phoenix.
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:
The thousands of people that showed up for me in Phoenix were amazing Americans. @SenJohnMcCain called them "crazies"--must apologize!
- Donald J. Trump (@realDonaldTrump) July 16, 2015.@SenJohnMcCain should be defeated in the primaries. Graduated last in his class at Annapolis--dummy!
- Donald J. Trump (@realDonaldTrump) July 16, 2015