The Trump Train hasn't fallen off the tracks — but the engines might just be stalling out. The candidate who is seemingly unable to be derailed by controversy has seen his campaign significantly hurt after he attacked the Muslim parents of a fallen U.S. soldier. 

A quick recap: the parents of Humayun Khan, an Army captain who was killed in Iraq in 2004 by a suicide bomber, spoke out last week against Republican presidential nominee Donald Trump at the Democratic National Convention. Humayun's father Khizr Khan was responsible for one of the more memorable speeches at the event, questioning if Trump had even read the constitution and saying he had sacrificed nothing. Trump responded by criticizing Khizr, mentioning he sacrificed by having business success and by suggesting Humayun's mother Ghazala was not allowed to speak as Muslim. (Ghazala responded by speaking out against the GOP nominee, saying she did not talk at the DNC because she was consumed with grief for her son). 

Trump has been condemned for his criticism of the family from both sides of the political aisle, resulting in a real fallout. The campaign fired Monday senior adviser Ed Brookover, who acted as the middle man between the campaign and the Republican National Committee, Reuters reported. Sources reportedly would not reveal the reasoning behind the move and a statement said the campaign was "thankful to him for his many contributions and appreciate his continued support."

The Kahn controversy has folks on the right concerned. U.S. Rep. Richard Hanna, a three-term New York Republican, became the first GOP Congressman to announce he would vote for Democratic nominee Hillary Clinton over Trump. Hanna specifically cited Trump's attacks on a Gold Star Family — meaning those who lost a son or daughter in combat — as a reason for the move. 

"I saw that and felt incensed," Hanna said in an interview with Syracuse's Post-Standard. "I was stunned by the callousness of his comments."

Respected GOP strategist Sally Bradshaw — who helped write the party's now-famous autopsy that called a focus on inclusion after Mitt Romney lost in 2012 — said she planned to vote Clinton as well.  

But concerns extend further than a few GOP officials abandoning ship. As the Washington Post pointed out, critiquing the families of a soldier who sacrificed his life for the United States — Humayun Khan was posthumously awarded a Purple Heart and Bronze Star for the act that likely saved the lives of fellow soldiers — might be a bridge to far, even for Trump. 

"Nobody minds when he attacks other politicians; in fact, they like it. He’s instilling an ­accountability that doesn’t exist. But they don’t like it when he goes after real people, and they wish he would stop," said GOP pollster Frank Luntz told the paper. Luntz conducted a focus group about Trump with voters Friday in Columbus, Ohio.

Groups nationwide have spoken out against Trump for the comments, including the Veterans of Foreign Wars and a group of Gold Star Families, both of which demanded an apology. Trump has not obliged. The fallout also might be showing in the polls, where the GOP nominee has fallen behind Clinton, who saw a post-convention bounce upward.