Moral foundation theory has generated a whole cottage industry of researchers studying the relationship between moral intuitions and political identity. According to this theory, moral judgments are based on five innate moral intuitions: Care/protection from harm, Fairness/reciprocity, Loyalty/ingroup, Authority/respect, and Sanctity/purity. . Theorists propose that different political sensibilities reflect variations in the strength of each moral intuition. Most of the research has been done on self-described liberals and conservatives in the US.
Both "liberal" and "conservative" are labels of convenience. They are ideal types with some predictive value yet they gloss over a complicated reality. For instance, conservatism is associated with the Republican party, but most Republicans are not consistently conservative; they hold a mix of conservative, moderate and liberal views, as this recent Gallup survey shows:
Ignoring this complicated reality, pundits and partisans have embraced the idea that pure conservatives and liberals are commonplace in the US, both with distinct moral profiles. To simplify: conservatives are heavy on Loyalty, Sanctity, and Authority and liberals are big time in the Care department. I know many progressives who are quite taken with this apparent division of moral labor. For them, Care - aka compassion - is the moral virtue that matters; Loyalty, Sanctity, and Authority are lesser gods, leftovers from an earlier, darker, age.
I've always been skeptical of these generalizations. Just because people are willing to label themselves as conservative or liberal doesn't mean conservatives and liberals are homogeneous groups. Significant findings on the association between moral intuitions and political attitudes may be driven by subgroups and not apply to most members of the larger group. For instance, Loyalty, Sanctity, and Authority are likely to be strongly valued by religious/social conservatives but not so much by socially liberal/economic conservatives*. But both may be comfortable calling themselves 'conservative'.
Another issue is that a two-part political typology hardly exhausts the range of American political opinion. There are, for instance, libertarians. Where would you locate libertarians on the liberal-conservative continuum? Do the five moral intuitions really capture the moral foundation of libertarian values?
Next: A new moral intuition to make sense of libertarians.
* Pure speculation: to the extent that religious/social conservatives hang out or otherwise communicate with other conservatives, the latter may gain an appreciation of the former's moral principles and this appreciation may nudge their own moral intuitions in a more socially conservative direction. Atheists living among nice religious folk may warm to the values of their neighbors without converting to their religion.
Reference:
Haidt, Jonathan (2012). The Righteous Mind: Why Good People are Divided By Politics and Religion. New York: Pantheon Books. pp. 9–11. ISBN 978-0-307-37790-6.