The battleground over abortion is shifting to Tennessee, where campaigns are heating up on a referendum that is a year away.

The referendum, pushed by anti-abortion groups for years, would add an amendment to the state constitution stating, "Nothing in this Constitution secures or protects a right to abortion or requires the funding of an abortion." The amendment would apply to all abortions, including those stemming from "circumstances of pregnancy resulting from rape or incest or when necessary to save the...