Gov. Ron DeSantis of Florida paused, looked down and then told a banquet hall filled with conservative Iowa Christians something that he had never before said in public: His wife, Casey DeSantis, experienced a miscarriage several years ago during her first pregnancy.

The couple, Mr. DeSantis explained on Friday at a forum for Republican presidential candidates hosted by an influential evangelical group, had been trying to conceive before taking a trip to Israel.

“We went to Ruth’s tomb in Hebron — Ruth, Chapter 4, Verse 13 — and we prayed,” Mr. DeSantis, citing Scripture, said at the event in Des Moines. “We prayed a lot to have a family, and then, lo and behold, we go back to the United States and a little time later we got pregnant. But unfortunately we lost that first baby.”

The deeply personal revelation — in response to a question about the importance of the nuclear family — was an unexpected moment for Mr. DeSantis, who is usually tight-lipped about both his faith and his family life. On the campaign trail, he rotates through a limited set of anecdotes about Ms. DeSantis and their three young children, as well as his religious beliefs. Still, at the Iowa event, he lingered only briefly on his wife’s miscarriage, calling it simply a “tough thing” and a test of faith.

Mr. DeSantis, a Roman Catholic, is heavily courting Iowa’s religious right, which has helped deliver the state’s last three competitive Republican presidential caucuses to candidates who wore their faith on their sleeves. White evangelical voters are likely to play a decisive role in the state’s Jan. 15 caucuses, the first contest in the 2024 G.O.P. primary, and they often turn to politicians who speak the language of the church.

“You have to talk authentically from the heart,” said Terry Amann, a conservative pastor from Des Moines. “Anybody can cite Bible verses.”

If Mr. DeSantis has any hope of beating former President Donald J. Trump, the front-runner, who leads him by roughly 30 points in Iowa polls, it lies in winning over conservative Christian voters while fending off the challenge of Nikki Haley, the former governor of South Carolina, who is seen as more moderate.