The political world is in an uproar about Donald Trump's attack on John McCain. Disparaging McCain's military record will be a major inflection point in Trump's campaign, some say, the moment when his bubble of popularity begins to deflate. Rival candidates say Trump's remarks disqualify him from serving as commander in chief.

But for the actual voters who were in the room when Trump spoke to the Family Leadership Summit in Ames, Iowa, Saturday, it's possible Trump's greater sin has nothing to do with McCain. Instead, Trump's casual and disengaged characterization of religious faith may have made a far worse impression on the mostly evangelical conservatives who came to hear Trump and other Republican hopefuls speak.

If a candidate wants to make a good impression on religious voters in Iowa, he probably should not offer the answer Trump gave when moderator Frank Luntz asked whether Trump had ever asked God for forgiveness. "I am not sure I have," Trump said. "I just go on and try to do a better job from there. I don't think so. I think if I do something wrong, I think, I just try and make it right. I don't bring God into that picture. I don't."

A candidate who seeks to make a good impression should also probably refrain from describing Holy Communion in the way Trump did: "When I drink my little wine — which is about the only wine I drink — and have my little cracker, I guess that is a form of asking for forgiveness, and I do that as often as possible because I feel cleansed. I think in terms of 'let's go on and let's make it right.'"

A senior Iowa Republican who was in the room, sitting with a group of grassroots activists as Trump spoke, was dumbfounded by the candidate's views of religion. "While there were audible groans in the crowd when Trump questioned whether McCain was a war hero," the senior Republican said via email, "it was Trump's inability to articulate any coherent relationship with God or demonstrate the role faith plays in his life that really sucked the oxygen out of the room.."

The senior Republican continued: "Milling around talking to activists in the hallways/lobby after Trump's speech, THAT is what those Iowa conservatives were discussing, not the McCain comment."

New York Times reporters Jonathan Martin and Alan Rappeport noticed the same thing: "It was these comments, not his attack on Mr. McCain, that prompted the most muttering and unease in the audience."

Attendees told the Times that Trump's casual use of the words "damn" and "hell" made a bad impression. "I was turned off at the very start because I didn't like his language,'' one woman who had been considering supporting Trump told the paper. Admitting he never asks God's forgiveness didn't help. ''He sounds like he isn't really a born-again Christian," the woman added.

What will be the result? Another Iowa activist — this one supports a rival campaign — said Trump will suffer, not with his core supporters but with potential supporters, like the woman who spoke to the Times. "I think that Trump will keep all the voters who were thinking of him as their first-choice, because they are not the kind of people who care about political discretion, measured words, or being sensitive to how one comes across," the activist said via email. "They just wants heads to roll. They are the 'throw the bums out' crowd who are sick and tired of politicians."

"I think that Trump will lose a percentage — maybe one-third to one-half — of voters who would have considered him as their second choice. And he will lose all the voters who would have considered him as their third choice."

That's an analysis spoken by a true veteran of Iowa caucus politics. For his part, the senior Republican sees damage, too — but not so much for the reasons that have upset national analysts. "Trump's performance was really a one-two punch," the Republican said. "His McCain comment gave free license to other candidates and the national political class to attack. His failure to demonstrate even the most rudimentary understanding of leading a faith-filled life will be his ultimate undoing with Iowa's Christian conservative activists. Especially in a field with such credible alternatives."