Why, the perplexed talk-show host asked last week, would the Democrats expunge all references to God from their party platform? And why reverse the party’s position that Jerusalem is the capital of Israel? How, he wondered, could this ever have happened?

Good questions. To help answer them, I turned to the Pew Research Center’s American Values Survey, one of the best ongoing surveys of where Americans stand on a wide variety of public-policy issues and the values that underlie them.

The short answer is that a “big sort” has been unfolding for more than two decades, and it has transformed the Democratic and Republican parties into two competing ideological camps. More Republicans than ever identify as conservative, just as a record number of Democrats say they are liberal. Almost entirely gone are the political hybrids known as “Rockefeller [i.e., liberal] Republicans” and “Boll Weevils” or “Blue Dog [i.e., moderate to conservative] Democrats.”

More to the point, Pew’s data demonstrate that Americans have sorted themselves into these two political tribes according to vastly different attitudes toward religiosity and morality. This divide makes it increasingly easy for one tribe to propose and do things that strike the other as downright incomprehensible.
According to Pew, between 2000 and 2012 the following ideological shifts occurred within the two parties:

 percent of members who are conservatives

    2000   2012
GOP     60      68
Dem     24      20

 percent of members who are liberals

    2000   2012
GOP      7       5
Dem     28      38

Looked at another way, during the 2000 election, Democrats were a surprisingly diverse lot, ideologically speaking, with nearly equal blocs of conservatives (24 percent) and liberals (28 percent). Twelve years later, the ratio of liberals to conservatives was nearly 2 to 1 (38 percent to 20 percent). While 38 percent may not sound like a saturation level of liberals, it is twice what virtually every national poll finds to be the liberals’ share of the electorate.

The story was different within the GOP, where the ideological ascendancy of conservatives was already well established by 2000. Even then, conservatives outnumbered liberals in the party by more than 8 to 1 — 60 percent to 7 percent. Three presidential-election cycles later, the ratio has grown even more lopsided. Conservatives have achieved near-monopoly status in the GOP, outnumbering liberals by nearly 14 to 1 (68 percent to only 5 percent).

The American National Election Studies (ANES), a series of surveys conducted jointly by Stanford University and the University of Michigan, reinforce all this. ANES found that, in 2008, fully 88 percent of liberals had found a political home in the Democratic party, while 76 percent of conservatives are now card-carrying Republicans.

This ideological sorting process is evident on matters of religiosity and faith. Twenty-five years ago Democrats and Republicans were virtually indistinguishable on matters of faith; today a gap has emerged that explains the miscues that were on display at the Democrats’ convention.

A quarter-century ago it was hard to find Democrats who doubted the existence of God, questioned whether we will be “called before God at Judgment Day to answer for our sins,” or subscribed to the Modern Family view of family and marriage. As recently as 1987, only 9 percent, 12 percent, and 14 percent, respectively, of Democrats dissented from these traditional values. Now 22 percent of Democrats doubt the existence of God; 26 percent are skeptical about Judgment Day; and 37 percent reject “old-fashioned views on family and marriage.” Among liberal Democrats, who dominate the ranks of party activists, support for the traditional view of family and marriage has plummeted steadily over this period, falling from 81 percent in 1987 to 67 percent in 2002, 53 percent in 2007, and only 44 percent today.

Given the nature of how party platforms are drafted and whose voices are most often heard, it is entirely understandable that the Democrats’ drafting committee heard only from the liberal voices within their coalition. But take note. As much ground as the Left has gained on these issues, they remain a distinct minority even in the Democrats’ coalition, outnumbered by fellow Democrats who remain more traditional in their religious and social views. It was likely those traditional Democrats who, on learning of the changes, reared up and forced party leaders to retreat.

Who are these traditional-values Democrats? One hint: Overwhelming majorities of African-Americans remain wedded to these widely held views. Fully 91 percent say prayer is “an important part of their daily life”; 89 percent “never doubt the existence of God”; and 87 percent both expect to be called before God on Judgment Day and believe that there are “clear guidelines about what’s good or evil that apply to everyone.”

— Michael G. Franc is vice president of government studies at the Heritage Foundation.