An increasingly obvious feature of American politics over the past quarter-century has been the prominent and polarizing role played by religion. The strategic importance of evangelicals and of religious people in general has burgeoned to the point where a presidential campaign (namely, George W. Bush’s in 2004) scorned the conventional wisdom of courting undecided, middle-of-the-road voters and triumphed instead by turning out its church-going base.

Church attendance now more closely predicts liberal-conservative voting patterns than wealth or class. Party platforms and election strategies shape themselves to a red-state/blue-state divide, with the Republican Party winning by a margin of passionately religious-minded voters who cite moral concerns as their chief reason for voting. Why has this happened? And why didn’t it happen a generation or two ago?

In a recent social-science research project, Harvard economists Edward L. Glaeser, Giacomo A. M. Ponzetto, and Jesse M. Shapiro applied economic theory and statistical analysis to political decision making in the United States and other democracies around the world. Their goal was to explain politicians’ use of “strategic extremism,” the choice of an extreme political stance designed to attract more voter support. (The word “extreme” here bears no pejorative meaning; it simply describes a policy option at one end of the spectrum of ongoing debate.) Their paper, titled “Strategic Extremism: Why Republicans and Democrats Divide on Religious Values,” bristles with sophisticated mathematical analysis, but the basic argument can be articulated in plain language. It delivers a surprising perspective on the role of religion in politics, as well as, perhaps, a caution to Catholics on the risks involved in uncritically translating faith into political action.

How does political extremism work? To answer this question the Glaeser study employs the economics of information. It is well known that voters tend to be energized by extreme political positions; research shows turnout higher among those who agree with a candidate on one or a few issues they care about intensely than among those who share a broader but milder agreement. But in order for a candidate to help himself by adopting an extreme position, it must have a larger positive effect on his supporters than the negative effect it has on others. Hence the prevalence of direct-mail marketing, Web sites, TV ads tailored to particular audiences, and invitation-only rallies, all of which ensure that a candidate’s extreme message will be heard by more of his supporters than his opponent’s—what social-scientific jargon calls an “asymmetric” reception of information. Politics is not just about getting your message out, but about whom you get it out to. Few messages can be perfectly targeted, so extreme messages do get heard by some voters who are turned off by them. For an extreme message to be successful, it must be effectively targeted so it fires up supporters more than it incites others to work for the opposition.

Now the question arises, which groups make the most attractive targets? The authors argue that if a particular group is too small, say only 10 percent of the overall electorate, the gains in enthusiasm of the few may be offset by a more broad-based negative reaction in others who may also hear the extreme message. Such a group, in other words, is not big enough to reward political extremism; its favorite issues will hold little importance in the political fray. On the other hand, if a group is too large—say, 70 percent of the electorate—it will often include many of the opponent’s supporters, who will have as intense a negative reaction to an extreme message as the positive reaction of the candidate’s supporters. In this case, the group “no longer creates the opportunity for the transmission of targeted messages”; it isn’t small enough to be uniform. And from an analysis of political data in many nations, the authors arrive at the somewhat counterintuitive notion that for a group to be ideally useful as a target for extreme political messages, it must have a moderate size—about 45 percent of the overall electorate, to be precise. For example, labor unions in the United States used to be large enough to lead politicians (in this case, Democrats) toward strategic extremism on economic issues. But no longer. Union membership has dropped to less than 15 percent today, and, as a result, fiery class rhetoric aimed at union members is not productive. The shrinkage of the unions has eliminated their clout, the model says; in effect, union members are too few to be worth catering to.

Churchgoers, on the other hand, find themselves highly popular. The Harvard study correlates the gradually shrinking size over recent decades of America’s churchgoing public—defined as those persons who attend church at least once a month—with its growing tendency to embrace Republican policy positions. (We should note that the model does not explain why most Republicans or most Christians vote the way they do; it analyzes the political function of groups, not the particular content of their beliefs.) Churchgoers generally are more likely than the national average to vote Republican. But in states where a higher proportion of the public attends church (for example in the Carolinas, where more than 60 percent do), churchgoers include a lot of Democrats, and—just as the model predicts—the correlation of church attendance and voting Republican is weaker than the national average. In states with lower rates of church attendance, on the other hand, such as Washington and Oregon, there is a higher correlation between church attendance and support for the Republican Party. (The study notes that Utah is an anomaly here.)

It is no coincidence, the authors argue, that religious extremism in U.S. politics has been on the rise as the proportion of church-going Americans has dropped, from 57 percent in 1968 to 49 percent in the 1990s. Few issues better exemplify the role of religion in politics than abortion, and it is illuminating to examine the change in rhetoric over time. The 1976 Republican Party platform advocated “a continuance of the public dialogue on abortion” and supported the “efforts of those who seek enactment of a constitutional amendment.” Twenty-five years later, the Republicans declared that “the unborn child has a fundamental individual right to life which cannot be infringed.” When it comes to politics, then, preaching to the choir can and does pay off—as long as the choir is the right size, not too big and not too small. American churchgoers get the attention of politicians, the Glaeser study suggests, because at this particular moment in time, they are sized just right to be useful to the politicians.

But are politicians useful to churchgoers? Has the churchgoing public’s large political investment in moral issues, especially abortion, been duly rewarded? The Harvard study proceeds to assess the relationship between rhetoric and action in the politics of extreme positions. It points out that one can usually determine whether conviction or strategy motivates a politician to take a particular extreme policy stance. If the stance arises from personal conviction (“nonstrategic extremism”), then actions taken in support of it will typically be more extreme than the rhetoric of the campaign. If a stance arises from strategy, though, the campaign message will be more extreme than the policy actions ultimately taken. In layman’s terms, strategic extremism is more bark than bite.

Let us examine how this applies to the politics of abortion. For all the principled talk about the right to life, the evidence suggests that opposing abortion is a strategic issue for the Republican Party. Republicans have held the White House during five of the seven four-year presidential terms since 1980, and have controlled one or both houses of Congress through most of that time. Has the party ever really made abortion a legislative priority? The number of abortions has remained about the same under Democratic and Republican presidents, even apparently rising somewhat since George W. Bush’s election. Republicans remain perennially the champions of Christians opposed to abortion—without actually bringing about any change. (Even partial-birth abortion legislation doesn’t reduce the number of abortions; it just requires that another method be used.) President Bush puts far more personal energy and White House clout behind tax cuts and Social Security “reforms,” and it is hard not to interpret his tepid follow-through on abortion as a Republican attempt to retain the support of its religious coalition without taking substantive action on the issue.

The implications of the Glaeser study suggest that Christians and especially Catholics must address the danger of being used strategically by politicians who pander to a passionate moral conviction for their own gain, then don’t deliver the goods. Are we being taken in by a tactic disguised as a value? What’s clear is that by making abortion the sole or primary focus of their political involvement, Catholics today have become known in American politics for a range of issues far narrower than can be warranted by Catholic moral theology. The faith that is our birthright testifies to the richness of a lifelong fabric of justice and love. And yet we often throw our support to politicians who themselves don’t support the church’s commitment to a broad range of justice issues. The economic policies pursued by the Republican Party are considerably more extreme—to the benefit of the wealthy—than their campaign rhetoric would suggest. According to the Harvard study, this means that unlike their stance on abortion, the Republicans’ economic policies are pursued out of conviction. When it comes to defending the interests of the rich, they talk softly but carry a very big stick.

For Catholics, the question boils down to this: How many decades of inaction on abortion would be sufficient evidence for us to conclude that political mobilization on the issue is a misuse of scarce ecclesial resources—resources that should be directed to support a wider range of goals? With the appointment of a new chief justice for the Supreme Court, and the nomination of Harriet Miers to replace Sandra Day O’Connor, it is possible that the new Court will overturn Roe v. Wade. But if the Court does not overturn Roe, will Catholics then decide they’ve misallocated their political capital?

Some will reply that unsuccessful efforts in support of a just cause are warranted, even necessary, perhaps, for living a moral life. But those who recognize that politics is “the art of the possible”—and that moral people can at times be badly used in the political process—may better conclude that moral responsibility requires accountability for a broad range of issues. Perhaps the primary lesson here concerns the dangers of moral perfectionism in politics—the difficulty of making a simple translation from personal moral priorities (even those demanded by the gospel) to political priorities. Reinhold Niebuhr, one of the most perceptive political observers of the twentieth century, chided the churches for their naive encounters with worldly power-particularly political power. As Niebuhr put it, pressing moral perfectionism in politics “smells of dishonesty,” and Christians who heed the siren song of politicians’ moral rhetoric all too often end up “the witting as well as unwitting tool of class interest.” If Catholics are indeed being manipulated on abortion, it would be time for a change in strategy by the bishops and laity alike.

Moral perfectionists take the position that if abortion is the most fundamental moral issue today, then striving for political change on abortion should outweigh pressing for change on all other issues. So powerful and pervasive is this mistaken belief that I would not be surprised if at least some of these moral perfectionists misunderstand this essay and claim that it indirectly advocates abortion simply because it questions the political judgments the church has made in opposing abortion.

The challenge here lies in the relation between the importance of the goal and the effects of our efforts. Thomas Aquinas observed that some evils are condemned by God’s revealed law but are not and should not be forbidden by human law, “since while aiming to do away with all evils it would do away with many good things and would hinder the advance of the common good.” Moral perfectionism in politics ignores Aquinas’s view that both effects and intentions are important, and instead turns the perfect into the enemy of the good. Priority in the political process should arise from an interplay of moral importance and political effect.

Fundamental values should, of course, be protected by law. But in our efforts to use public policy to do so, good Catholic moral theology and Aquinas himself require that we avoid the pitfalls of singlemindedness. A recent case for consideration is the role of the U.S. delegation to the March 2005 Women’s Conference at the UN. At a conference focused on the abuse of women around the world—where issues on the agenda included such horrors as sexual slavery and rape as a war tactic—the Bush administration held up progress for several days by insisting that a statement against abortion be included in the conference document. A principled stand? The economic analysis of strategic extremism suggests that although the Bush team knew from the start that the antiabortion plank would not ultimately be included, they made the effort simply to garner support from prolife voters back home. Yes, those who consider abortion wrong want to work to minimize it. But surely it is morally wrong of this administration to stall progress on eradicating sexual slavery and war rape merely to broadcast a very public restatement of its already well-known stance on abortion. And shouldn’t prolife voters criticize the administration for inappropriately pressing abortion at this conference where even the official Vatican statement never mentioned the issue?

Let me be clear. Strategic decision making by officeholders is an inevitable part of democratic life and is not in itself an evil. Indeed, Christians can and should learn how better to employ the political influence of citizens’ groups to press their elected leaders for a morally vigorous stand on issues ranging from abortion to health care to the war in Iraq. Nor do I wish to imply that Christians shouldn’t deal with politicians who have merely strategic reasons for cooperation. Similarly, I do not intend to take Democrats off the hook on abortion. They have too often sided with extreme voices, badly overstating the claims of individual autonomy. The point here, though, is to put both parties on the hook for the full range of issues that Catholic moral analysis addresses.

In sum, the Glaeser study suggests to us several cautions. The first is that prolife Christians who take religious perfectionism into politics act irresponsibly if they do not count the moral cost of demoting other issues of Catholic social thought. The second is that while Christians may take moral perfectionism into politics, the politicians appealing for their support surely do not. Decades of political promises without discernibly different results for abortion under Republican and Democratic administrations should be treated as prima facie evidence of the strategic use of Catholics and other Christians by politicians whose narrow interests are served by allowing the current impasse on abortion to continue while appearing to work for a resolution. Statements of support come cheap; pay attention to results.

The Harvard study tells us that demographic declines have made U.S. Christians attractive targets for strategic manipulation by politicians bent on reaping political gain from their constituents’ moral convictions. The study implies that if the shrinkage continues apace, at some future date such a group may become too small to be pandered to. But for the time being, get used to it: voters’ passionate convictions are the ticket to election. So when it comes to taking one’s faith into the voting booth, be forewarned. Caveat credens. Let the believer beware.

Related: Goodbye, Catholics: How One Man Reshaped the Democratic Party, by Mark Stricherz