Pete Buttigieg, the Indiana Democrat waging a long-shot 2020 bid for the presidency, explained why he has called into question President Donald Trump’s Christianity.

Buttigieg, a gay Episcopalian who has been outspoken about his progressive Christian values, has been critical of the ways in which Trump and Vice President Mike Pence show their faith.

In a USA Today interview published Wednesday, Buttigieg said it is hard for him to look at the actions of Trump, a professed Presbyterian, and “believe that they’re the actions of somebody who believes in God.”

“I just don’t understand how you can be as worshipful of your own self as he is and be prepared to humble yourself before God,” Buttigieg, the mayor of South Bend, Indiana, said in the interview. “I’ve never seen him humble himself before anyone.”

Buttigieg also has questioned how Pence, who calls himself an “evangelical Catholic,” allowed himself to become a “cheerleader of the porn-star presidency.”

“Is it that he stopped believing in scripture when he started believing in Trump?” Buttigieg said at a CNN town hall in March.