These are very good posts. I have one nit. If I understand my history correctly, the evangelicals had been Democratic since well before the FDR days. Those in the South of course were Democrats since before the Civil War. The evangelicals in the plains areas were the core of Williams Jenning Bryan and his "prairie populism", a theme explored in the recent book "What's the Matter with Kansas".
To clarify another point, prarie populism was itself a new development, a post-Civil War thing, in its essence. Bryan himself was born in 1860, the year the Civil War 'turned hot' and his generation was animated by post-Civil War concerns. It was manifestly not simply a development of pre-Civil War religious movements, though it drew on them to some extent, it was a new thing.
It left its mark, and in fact was one of the strains of thinking that went strongly into the FDR political coalition/national consensus. The Democratic Party that emerged from the Great Power Crisis was in many ways the product of Bryan's thinking, it incorporated much of it. Yet it also incorporated a great many things Bryan would have hated, and it was quite different from the Democratic Party of 1900.
(Today, Bryan is often unfairly and mendaciously seen as a figure of ridicule due to the widespread misreprensentation of his views and the nature of the Scopes Trial, in fact he was one of the most influential political/social figures in American history.)
We look back at 'prarie populism' today, from a century later, and it looks like an obvious development, a concise, contained thing. That's a view we impose on it in hindsight, an attempt to package messy reality into neat categories and labels.
That's not how it looked to the people doing it, it was uncertain, vague, they didn't necessarily think of themselves as part of something bigger, because they weren't at the time. The outcome was never fore-ordained, things could have turned out differently. The 'populists' themselves often had wildly varying agendas.
The Boom Awakening* brought new changes that have yet to gell, including a new attitude in the religious conservative faction. There are major differences in mindset between the G.I. and Silent people of faith and Boomer and younger ones, even as they agree on most of the theological basics, just as post-BAwakening feminists are not the feminists of Eleanor Roosevelt or Elizabeth Cady Stanton (themselves women of different times and mindsets).
Here is an example of these changes. In the period between the Civil War and World War II, what was then the equivalent of the 'religious right' and their fellow travellers were more or less allies of the feminist movement of that time, and both were (again more or less) allies of the labor movement. All three had many interests in common, and they seemed like natural allies.
That's not the say they didn't have their differences, but overall they were pulling in more or less the same directions. Living wages, safety regulations, an end to child labor, Prohibition, certain strains of anti-war pacifism (but only certain strains), and other issues were often backed by all of them.
Prohibition, for ex, was very much a feminist issue in the early 20th century, as well as a religious one, it was seen both as a sin and it was also seen as a primarily male vice that led to the mistreatment of women and children and the destrution of family life. That connection is often forgotten or overlooked today, since it has no matching parallel in today's debates.
(If we're not very careful, there's a natural tendency to look to the past to find things parallel to today's controversies, and dismiss the rest as minor or unimportant, when in fact those dismissed aspects might have been the ones our ancestors cared most about.)
One of the things the Boom Awakening did was shatter tha connections between the labor movement, the feminist movement, and the religious right, using those labels very broadly. The fracture happened to a large extent during Carter's tenure, and though he didn't cause it, his policies helped it along. A side-effect of the fracture is that today's competitors tend to forget that they were once allies.
Another side-effect is that since all these groups, or rather their antecedent groups, were part of FDR's grand national consensus/coalition, they all tend to see themselves as being the embodiment of the national tradition and heritage, and to see their former allies as having abandoned that, or turned against it, which is part of why so much resentment exists between them. Each one sees themselves as defending the basic essence of what America is against factions that have betrayed, and even actively attack, what America means. They tend to overlook how big the changes in their own goals have been, all of them.(The labor movement being an exception, because currently it's totally comatose. That may be starting to change, though.)