Republican presidential candidate Donald Trump is not apologizing for his harsh comments about Sen. John McCain's Vietnam War service, issuing two new tweets blasting the 2008 GOP presidential nominee's work with veterans and criticism of Trump's followers as "crazies."

Despite indications that his comments against McCain were turning off supporters, Trump tweeted that McCain hasn't helped veterans during his time in the Senate.

"The Veterans Administration is in shambles and our veterans are suffering greatly. John McCain has done nothing to help them but talk," he tweeted out Sunday morning.

And he took offense at McCain's comments that Trump has tapped into the "crazies" with his get-tough talk on immigration.

"John McCain called thousands of people 'crazies' when they came to seek help on illegal immigration last week in Phoenix. He owes apology!" he tweeted.

Both were promoted on Trump's campaign homepage.

Clearly Trump is doubling down on his assault on McCain even as reports, like this story from the Examiner's Ryan Lovelace, show that some voters in Iowa are backing off their support from Trump after he suggested military prisoners of war don't rank as war heroes.

Paul Bedard, the Washington Examiner's "Washington Secrets" columnist, can be contacted at pbedard@washingtonexaminer.com.