ANKENY, Iowa — Roman Catholic leaders in the early voting state of Iowa implored candidates for president Thursday to take up Pope Francis’ call for “profound political courage” by focusing their campaigns as much on improving the environment and income inequality as they have on opposing gay marriage and abortion in past elections.

The vocal pivot from such traditional social issues marks the first time U.S. Catholic bishops have publicly asked those seeking the White House to heed the admonitions of Francis’ June encyclical, said Bishop Richard Pates of Des Moines.

In Francis’ major teaching document, the leader of the world’s 1.2 billion Catholics called for a “sweeping revolution” to correct a “structurally perverse” economic system that allows the rich to exploit the poor and has turned the Earth into an “immense pile of filth.”

“These are going to be difficult decisions that have to be made,” said the Rev. Bud Grant of Davenport, joined at a news conference by bishops from central and eastern Iowa. “Politicians have to have the courage to do the right thing, and not necessarily the politically expedient thing.”

The push from bishops threatens to disrupt the historically reliable alliance of evangelical Christians and conservative Roman Catholic voters, putting pressure on Republicans who have leaned on their religious faith to guide them on social issues.