What follows is not in any way scientific. I have no training in the science of statistics anyway. I’m not sure it can even be called an educated guess. But it’s more than just a shot in the dark. It’s an estimate based on a lot of anecdotal experience. I “get around” some in the Episcopal Church.
On the “far left”—there are certainly some Episcopalians who would have to cross their fingers in a big way to say the creed. They are not at all committed to traditional theological categories and language about such things as Incarnation, Atonement, Resurrection, or even the personal nature of God. They believe Jesus was the proverbial “great moral teacher” who “shows us how to live.” One honestly wonders (at least I honestly wonder) why such persons even call themselves Christians, let alone Episcopalians. The retired Bishop of Newark, John Shelby Spong, would be the poster boy for this category of Episcopalians. My guesstimate is that they represent 2%-4% of the clergy and maybe somewhere in excess of 5% of the laity, especially in the major urban dioceses.
Slightly to the right of this group is a class of Episcopalians who cross their fingers while saying the creed, but only loosely. They would affirm much of the language of traditional Christian theology, but substantially qualify their assent to the concepts themselves. They believe in some sort of personal God, and that Jesus is somehow an expression of that God, and that the world would be a better place if more people shared those beliefs. They are attached to the liturgical and sacramental ethos of traditional Christian practice, even while rejecting (or at least benignly neglecting) the underlying theology. Many of them are immensely faithful in worship and active in their parishes. Markus Borg and the Jesus Seminar would be the poster children for this group. My intuitive guess is that around 15%-20% of the clergy and a roughly equal percentage of laity fall into this category. However, they are collectively “louder” than many others, and, hence, it seems like there are more of them than there actually are.
Moving in the same direction, we next have a category of Episcopalians who can recite the creeds with a fair amount of integrity, and would certainly have a self-perception as “orthodox,” in that, by and large, they would wish to retain the language and categories that arose from the great Christological and Trinitarian debates of the third through fifth centuries. So they are not overly antagonistic to the Prayer Book—in fact, they have made something of a shibboleth of the “Baptismal Covenant”—and may profess genuine fondness for some very traditional elements of Christian spiritual practice (the Daily Office, spiritual direction, meditative prayer, for example), though most of them would want to delete, or at least significantly dilute—masculine pronouns about God, and other terms they consider loaded (Lord, Kingdom). They understand both theology and mission in largely social terms, as if everything the church does, in order to be authentic, must be ordered toward the unified objective of “peaceandjustice.” Ironically, while they observe institutional authority quite strictly much of the time, they have the capacity to sit very loosely to what might be called “meta-authority” in the church (like scripture and organic tradition). Both the Presiding Bishop and the Presiding Bishop-elect could stand as representative symbols of this group. I would suspect that something in the neighborhood of 50% of the clergy could be included in this category; it represents the paradigm that has been engendered in most of our seminaries for a number of decades now. However—and this might be the actual big story in my non-scientific analysis—I believe that only about half this percentage of laity fit such a description. There is a huge discrepancy here between the ordained leadership of the Episcopal Church and those entrusted to their pastoral care.
Sidebar: Without a doubt, virtually 100% of those in the above-defined groups would be at least conceptually supportive of the church providing blessing rites for same-sex relationships and removing any restriction on ordaining persons involved in such relationships, although some (less than a third, I would say) might be open to exercising restraint in those areas for the purposes of maintaining ecclesial communion.
Next we have a category that is diverse within itself—comprehending elements from both the Catholic and Evangelical (including the Charismatic) strains of Anglicanism—but is united in a transparent affirmation of both the language of the creeds and their underlying theology. The classical categories touching on human sin, the person and work of Christ, discipleship and growth in holiness make sense to them and energize their faith and practice. They are not “fundamentalist” in the popularly-accepted sense, in that they have a capacity for major-league scholarship and intellectual sophistication, and much of their theological expression can be quite irenic. While cautiously suspicious of modern biblical criticism, they do not dismiss its insights out of hand. They see themselves without affectation as the mainstream heirs of the Anglican tradition. Instead of a representative individual, I would suggest the periodical The Living Church as an appropriate emblem of this category. My intuitive guess is that nearly 30% of Episcopal clergy could be numbered here, but probably two-thirds of the lay membership, mirroring the discrepancy noted above. (Full disclosure note: I number myself in this category.)
Note: The great majority of Episcopalians in this last group would be opposed to the sort of blessings and ordinations that are favored by the other categories, though a relatively small number might believe that the subject is worthy of further exploration and discernment.
Finally, there is a small percentage of Episcopalians who might legitimately be labeled as fundamentalists. They would adopt an inerrantist view of scripture, believe in a literal six-day creation, and be adamantly hostile to the insights of modern biblical criticism. My sense is that this category might include 1% of the clergy and maybe 2% of the laity.
My point? We all need to be wary of using too wide a brush with which to paint our picture of the Episcopal Church. Simple (simplistic?) “two religions under one roof” analyses offer a certain appeal, but leave an awful lot un-accounted for.