Former Gov. Rick Perry is defending Donald Trump's war of words with the family of a fallen Muslim soldier, saying the father "struck the first blow" against the Republican presidential nominee and is not above criticism in return.

"In a campaign, if you’re going to go out and think that you can take a shot at somebody and not have incoming coming back at you, shame on you," Perry said in an interview Tuesday on CNN.

The father, Khizr Khan, harshly criticized Trump last month during the Democratic National Convention over the nominee's proposal to temporarily ban Muslim immigration. In the following days, Trump fired back by questioning why Khan's wife, who was standing beside him during his speech, did not speak, and arguing Khan did not have a right to attack him the way he did.

The episode brought Trump bipartisan condemnation, and it marked the beginning of a downward slide for his campaign that continues to this day. Perry's successor, Greg Abbott, issued a statement at the time saying the service of families like the Khans "cannot be questioned."

On Tuesday, Perry made clear he saw Khizr Khan as fair game. He insisted he admires veterans and their families but said the patriarch "politically used his time on that stage to go after Donald Trump."

"Why in the world that he thought he was going to get a free ride with that is beyond me," Perry said. "He shouldn’t get a free ride when he’s going to inject himself into the political arena."

Perry, who served in the Air Force, has been an outspoken advocate for veterans throughout his political career. He launched his own 2016 presidential campaign surrounded by military heroes, and after he dropped out last year, he went on to organize support for U.S. Sen. Ted Cruz, R-Texas, among veterans.

Perry, who called Trump a "cancer on conservatism" when he was still running against him, has avoided criticizing the nominee since he endorsed him in May. Before Trump tapped Indiana Gov. Mike Pence to be his running mate, Perry had said he was open to the job. Last month at the Republican National Convention, Perry expressed a willingness to serve in a Trump administration.

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