EARLIER this year, around the time when the papacy fell vacant, I interviewed the American Catholic writer George Weigel, a strong admirer of the conservative line set by popes Benedict and John Paul II. Something else he approves of, and has helped to foster, is the "theocon" alliance in American politics between Catholics and evangelicals, who have set aside their doctrinal differences (over the Virgin Mary, for example) to take a joint stand against abortion and in favour of the traditional family. That alliance has not gone away. Only the other day, a law-and-religion pundit wrote that for evangelicals, seeing a Catholic sit on America's Supreme Court was almost as good as having a member of their own ranks in that position. But the effectiveness of the Catholic-evangelical axis may be compromised by a deepening ideological fissure within the evangelical camp; or more specifically within America's largest Protestant denomination, the Southern Baptist Convention, which has about 16m members.

Broadly speaking, the difference is over whether Jesus Christ died to save mankind as a whole, or sacrificed himself only for a particular group of human beings, the elect, whom God had chosen in advance. The latter view is associated with John Calvin, the French reformer of the 16th century; critics find it too fatalistic, and inconsistent with the idea of a loving God. Taken to its logical extreme, some say, Calvinism can lead to an introverted, exclusive mindset: if most of humanity is irrevocably damned, what's the point of engaging with the world?

The perceived leader of the Calvinist camp is Albert Mohler, president of Southern Baptist Theological Seminary in Louisville, Kentucky. He has helped to ensure that many of the young Baptist ministers now starting their careers have a Calvinist way of thinking. In many cases they are out of their step with their flock, and that can lead to stormy pastoral situations.

Another Baptist campus, Louisiana College, has had a bumpy year after the president, in what was seen as an anti-Calvinist move, declined to renew the contracts of three faculty members. The president, Joe Aguillard, was then subjected to an investigation by his critics; and he denounced their tactics as "an attack plan" designed to stage a Calvinist takeover of the institution.

At last month's annual meeting of Southern Baptists, a report was presented which acknowledged differences—"we agree that God loves everyone and desires to save everyone, but we differ as to why only some are ultimately saved"—but stressed that all parties concurred on many basic axioms. Neither party will have the slightest truck with liberal ideas. But even among fundamentalists, there can be hard arguments over what the fundamentals are.

Will the outcome of this argument make a difference to anybody outside the world of Baptist theology? Yes, because as well as being hard-line over salvation, the Calvinists oppose any blurring of the boundaries between Christian denominations. So there are limits to their willingness to co-operate with higher-church Christians. "The Calvinists have a very anti-Catholic theological stand," I was told by David Key, director of Baptist studies at Emory University's Candler School of Theology.

Mr Mohler, for example, responded to the general excitement over the election of Pope Francis by recalling that evangelicals utterly rejected the Catholic idea that the pope was Christ's vicar on earth. In another statement, he said that Catholics and evangelicals might still agree on sexual and reproductive issues, but he also stressed that evangelicals could not accept the validity of the pope's office.

All this is taking place against a background of general declines in Southern Baptist numbers and in the political heft of the religious right. Don't be surprised if this trend is accelerated by intra-Protestant, and intra-Christian, quarrels.