Before he clinched the 2016 Republican nomination, won the presidency and remade the party in his nativist, norm-shattering image, Donald J. Trump lost the Iowa caucuses to a conservative Texan who had consolidated the support of evangelical leaders and voters in the state.

Eight years later, Mr. Trump is favored for victory in the Iowa caucuses on Monday, fueled by evangelical voters who have become among his most reliable supporters — and a more organized Iowa campaign effort that includes courting the kinds of religious leaders who helped propel Senator Ted Cruz’s victory in 2016.

Of Mr. Trump’s rivals, Gov. Ron DeSantis of Florida has been the most aggressive in trying to cut into that advantage, making outreach to conservative Christian voters a central plank of his Iowa strategy and winning over some prominent onetime Cruz backers despite struggling in the polls. Mr. DeSantis, who signed a six-week abortion ban in Florida, has also cast Mr. Trump as insufficiently supportive of abortion restrictions.

The former president has criticized the Florida ban, but has also often reminded voters that he made the Supreme Court appointments that led to the overturning of Roe v. Wade.

Nikki Haley, the former South Carolina governor, has not put the same emphasis on courting evangelical voters in Iowa, walking a careful line in particular on abortion rights as she seeks to emerge as the more moderate and mainstream alternative to Mr. Trump.

We spoke with some of the Iowa pastors who supported Mr. Cruz in 2016 to understand how they are thinking through their choices now.