One of the tragedies of the present age is the calcification of the Evangelical Church. Once a vital movement able to nurture diverse voices and promote ideas in the broader culture; once risking to talk about race now has come to be seen as one more cultural group, even a sect.
How did this happen? Many focus on histories and politics, but the underlying question is that of sociology, and yes of time.
Analyses of the Evangelical community stumble when they overlook the composite nature of this community. In 1976, there would have been four interacting communities, which together make up what we call Evangelicalism: the Fundamentalist South with its emphasis on eschatalogy and a separationist ecclesiology (Bible churches, the SBC); the Segregationist South, drawn from the PCUS now PCA community, the home of the segregationist academies (Randall Ballmer thinks of them as the origin of the Christian Right, well maybe); the Sunbelt Evangelicals, extending from Orange County to Dallas, less segregationist but militantly anti-communist, deeply engaged with conservative economics (SBC, Nazarene originally; the deep backers of Reagan); and the Northern protestant conservatives – often immigrant – see the split in the LCMS 1969, whose issues were the Bible but did not share believer baptism model of Sunbelt or Segregationist South.
Between abortion and Reagan they found common cause, but I don’t think we can see them as solely political in nature. The real power is cultural; the question is not history so much as sociology. In the 80s and 90s, these were the churches of the suburbs, the big boxes which developed a model of Christian life that focused on the family (and especially fathers — this the work of Kristin DuMez) at the same time that a certain anxieties swept through the Boomer generation as they raised their children. The characteristic nature of the suburbs of the day were white and moving upscale (e.g. Saddleback, Willow Creek); the churches reflect this as do their Christian schools. This cultural location opens a gap between Evangelicals and the urban and/or minority churches; it also made these same churches less attractive in the changing diverse nature of the new suburbs.
All this came to a halt with the changing nature of suburbanization (Tim Keller not withstanding), and the political choices in 2002-2004, a change well documented in such books as Amy Sullivan’s Party Faithful. Then add to the deindustrialization of the Midwest which tore the heart out of many small towns, The result is a cultural community that was largely outward facing in 1980-2002, turned inward, a defensive crouch, and with it the old reactions also took hold. As the northern wing shrank and the Sunbelt shifted the elements of Evangelicalism that remained standing were those of the South, meanwhile the kids leave town.