Beginning with Ronald Reagan in 1980, the GOP embraced the Christian Right and adopted increasingly pro-evangelical positions, including opposition to abortion, support for school prayer, and, later, opposition to gay marriage.
Since 1980, under Ronald Reagan's leadership, the Republican Party formed a strong alliance with the Christian Right, adopting more evangelical viewpoints. This partnership significantly shaped the party's policies, resulting in a firm stance against abortion and a promotion of religious practices in schools, notably supporting school prayer.
As this alliance strengthened, the GOP's positions shifted further, culminating in their opposition to same-sex marriage. This evolution within the party reflects a broader trend of intertwining political and religious ideologies, as discussed in Steven Levitsky's "How Democracies Die."