The Donald's going to have a hard time doubling down on this one. 

Politico is reporting that Trump, while speaking at a Family Leadership Summit in Ames, Iowa Saturday, told the crowd, "[Sen John McCain] was a war hero because he was captured. I like people who weren't captured." The two men had been engaged in a media war over the past few days.

Trump's slight was reportedly met with a scattering of boos from the crowd.

McCain was held captive in a North Vietnamese prison camp for five-and-a-half years, while Trump received four military deferments between 1964 to 1968.

UPDATE: Trump has posted a response to the backlash on his Facebook: