Objective. The research explores the impact of Roman Catholic and cons
ervative Protestant churches on state abortion policy. Methods. Data a
re state measures of membership in pro-life churches, abortion policie
s, interest group membership, public opinion toward abortion, and othe
r factors that previous research suggests may be relevant to abortion
policy. Results. Religion is a significant factor in abortion policy,
but not in simple ways. The impact of conservative Protestants is indi
rect, through public opinion: states with many evangelical Protestants
have more people with pro-life attitudes. In contrast, the impact of
Catholics is both direct and indirect: there is a direct pro-life impa
ct, that is not mediated by public opinion, which reflects the capacit
y to lobby state governments, and an indirect pro-choice impact throug
h provoking larger state memberships in the National Abortion Rights A
ction League in states with many Catholics. Conclusions. While there i
s one Roman Catholic church, with a diverse membership but unified lea
dership and doctrine on the abortion issue, there are many conservativ
e Protestant churches with no unified leadership. The authors suggest
that these structural differences account for the different ways conse
rvative Protestants and Roman Catholics influence state abortion polic
y.