Last month, Pew Research Center found that President Donald Trump had a 69 percent approval rating among white evangelical Protestants, compared to around 40 percent with the entire nation.

When the Republicans nominated the thrice-married serial philanderer with precious little knowledge of the Bible, some pundits took this as a sign of the weakness of the Christian right as a voting bloc within the Republican Party. If they could not stop what appeared to be their nightmare candidate, how much clout could they possibly have?

It turns out they have quite a bit of clout, considering they are currently the largest, most cohesive constituency in a party that cannot afford many defections or abstentions. Indeed, evangelical leaders have threatened to tell their flock to stay home or floated the idea of backing a third-party candidate multiple times over the past several decades.

In the 2016 Republican Iowa caucuses, evangelicals accounted for 62 percent of the electorate, and in South Carolina’s all-important 2016 presidential primary, they made up 67 percent. Trump and the Republican Party know they have to keep white evangelicals happy and deliver on promises made to win their votes.

Recent overtures to this group have included two staunchly pro-life Supreme Court justices, presidential addresses to the annual March for Life, and countless pieces of legislation designed to severely curtail a woman’s right to choose. Christian conservatives who recently despaired of losing the culture wars are newly emboldened, especially on the all-important issue of abortion.

This stunning about-face comes as a result of decades of grass-roots activity designed to entrench moral traditionalists in the Republican Party, from school boards all the way up to the White House. While the courtship of white evangelicals by President Reagan and both the Bushes has been well documented, how the Christian right worked their way into the guts of the Republican Party has been somewhat less studied. This is what I examine in my new book, Moral Victories in the Battle for Congress.

The ascension of white evangelicals within the GOP is a story of how party coalitions change. Across the nation, religiously conservative activists began in the mid-1980s to assert themselves by getting involved in local Republican Party politics.

In some places, their activity culminated in a hostile takeover of the formal party structure as in Sedgwick County, Kansas where, in 1992, two pro-life activists recruited hundreds of other activists to run for precinct committee chairmanships.

These newly elected officials went on to help oust the pro-choice party chair and replace her with one of the leaders of the insurgency. In other places, they set up informal, shadow organizations designed to wrest nominations away from the old guard Republicans. Either way, the path to power was clear: nominate new kinds of candidates — specifically those stressing moral traditionalism.

White evangelical activists transformed the Republican Party into one that was no longer solely focused on fiscal conservatism but that cared as much or more about culture war issues like abortion, LGBTQ rights, and the role of religion in public life

These new candidates were often recruited by local, grass-roots activists who in many locales saw a Republican Party that was at best lukewarm to their socially conservative stands and at worst downright hostile to them. These activists had to fight their way to prominence within the party by defeating more socially moderate, fiscally conservative GOP candidates in the primary.

Once those battles were won, it was onto the general election where the challenge was making moral issues count against often well-liked and popular Democratic incumbents. This transformed the Republican Party into one that was no longer solely focused on fiscal conservatism but that cared as much or more about culture war issues like abortion, LGBTQ rights, and the role of religion in public life.

My book profiles these intraparty battles in places like Sedgwick County, Kansas; Greenville-Spartanburg, South Carolina; and Chattanooga, Tennessee. The stories contained in these case studies illuminate much about American politics, including how party coalitions change and how issues interact with personalities and resources to determine electoral outcomes.

The intraparty battles that I highlight were between religious conservatives and fiscal conservatives. In Tennessee’s Third Congressional District, the Christian right first ascended to power in 1986 when they were able to defeat the local economic power structure’s favored candidate in the GOP primary. They nominated one of their own, activating the grass-roots by fixating on abortion and the personal religiosity of their candidate.

However, that contest was sufficiently divisive to doom the party to general election defeat. Eight years later, however, after much negotiation, the two factions agreed to join forces and were ultimately successful in flipping the Third District to the GOP as part of the 1994 Republican takeover of Congress.

By now, evangelicals have nominated enough candidates and won enough elections to become a dominant faction within the Republican Party. Evangelicals have remained incredibly loyal despite the myriad ways in which Trump has proven to be an unorthodox leader.

First and foremost, white evangelicals have been more than satisfied with Trump’s judicial appointments and his public statements on culture war issues. Second, Trump’s harsh rhetoric towards racial and ethnic minorities may not only be palatable to this constituency but secretly favored by many of them as well.

Their loyalty has been handsomely rewarded as an irreligious, libertine playboy has delivered more than his Republican predecessor in the White House who was a full-fledged born-again Christian. As Michael Corleone once said to his brother Sonny, “It’s not personal, it’s strictly business.” Christian conservatives in the age of Trump seem to be saying, “It’s not religious, it’s strictly politics.”

Marty Cohen is an associate professor of political science at James Madison University.