Conservative American Christians may agree on something like abortion, or homosexuality, but those are only public, civil morality issues*. On another level, though, a level which they think of as more essential, they're hotly opposed to each other.
This is maybe most clear in the noted distrust evangelicals have of Mormons -- a distrust voiced by Mike Huckabee -- but there're also less noted clashes. Southern Baptists, for example, have very different ideas about the Biblical role of women than do Sarah Palin's Assemblies of God. George Bush's Methodists are deeply uncomfortable with Pat Robertson's Pentecostals' beliefs about the active role of demons in the world. That's not even starting with Catholics**.
And the fact is, the theological groups bunched together under the heading "Religious Right" are the groups who are distinctive in large part because of their willingness to schism and split, to withdraw from cooperative and collaborative engagements and dissent from broad, ecumenical tolerance. A willingness -- even insistence -- on separating from those who believe differently is more characteristic of these groups than almost any theological point that could be articulated with any specificity.
This means a tricky, delicate move is necessary: Christian doctrines must, at once, be held as crucial for public positions, crucial for public officials, crucial for the country, and as irrelevant on the level of details. There's a just-enough-but-not-to-much that holds this thing together.
Look at how Christian Right 2012 presidential candidate Rick Santorum phrases it:
Voters should consider the candidate's moral framework and what they believe about right and wrong. Obviously your faith has a role in that, in constructing your moral view and your worldview, your ethical code. As far as theological tenets goes, those don't necessarily affect the public discourse. It's important to understand and know the tenets and teaching of the faith with respect to how people live their lives.The assumption that one's "moral framework" and "moral view" and "worldview" -- how evangelicals have come to love that once-relativisng idea! -- directly results in certain actions and decisions and programs could be considered more critically, but note, here, just how the argument is, in essence, that it matters and it doesn't matter.
There's a line somewhere in Santorum's mind where God and the Bible and Jesus stop being relevant to public issues. Which turns out to be necessary for a Catholic like him to join with Baptists and Mormons and Pentecostals in making theology relevant to certain public issues, like the legality of certain types of non-procreative sex***, or the way economics is taught in public schools.
This is one of the ways that talking about the Religious Right as theocratic, and mongering this fear about how they're plotting and designing a Christianist republic evidences a misunderstanding of the nature of this group****.
Pluralism is essential to their existence, even when they think of themselves as opposing it. The secular sphere and the idea of part of the the secular sphere where theological tenants have no effect is necessary even just to imagining how those tenants could have an effect somewhere else.
Theology in politics in today's America is tricky exactly because it can't be ruled out and also can't be ruled in. This is as true for the firm yet internally conflicted alliance of the Christian Right as it is for anyone else.
*It seems that the last time "conservative Christians" aggressively disagreed on an issue of public import and civic morality was slavery. This is very misleading, though, as it is largely these issues, as much as actual theological positions, that have come to define conservative Christians as conservative Christians, with certain public stands or issues functioning to mark one as "out," and thus not to be taken seriously. It's possible that prominent evangelicals such as Rick Warren taking positive positions on "liberal" issues like AIDS in Africa or global climate change could change this, so that one could be a conservative, squarely evangelical Christian and feel free to take a range of political positions, but we'll see.
**Though public policy cooperation has done more to reduce anti-Catholic bigotry in America than anything since Kennedy's civil beatification. As those most likely to be suspicions of the unAmericanness of Catholics and the unChristianness of Catholics now experience them as being co-belligerents in the moral crisis of the age, they're unlikely to conceive of them as subversive enemies in other areas.
***Now there's a really interesting example of how public policy agreements are not the same as theological agreement. Opposition to gay marriage is not the same as agreeing on what marriage is, or compatible theologies of sex.
****This is not to say there are no teeth to their positions. The ways they imagine and talk about reshaping American society can be extensive and significant.