DURING last week’s vice-presidential debate — the first time two Catholics have shared such a stage — a question about abortion was inevitable. To some viewers, Vice President Joseph R. Biden Jr.’s stance — that he personally opposes abortion but does not believe in imposing those beliefs on others — came across as a wishy-washy mélange of moral intuitions. In contrast, Representative Paul D. Ryan, who laid out his ticket’s policy to “oppose abortion with the exceptions for rape, incest and life of the mother,” appeared to represent the principled, Catholic anti-abortion position.

But while Mr. Ryan’s vision for abortion policy is far more restrictive than current law, it is not the one advocated by the Catholic hierarchy. Along with Mr. Biden, he has joined the ranks of dissenting Catholic politicians, those who preserve a distance between nonnegotiable Catholic moral teaching and civil law.

Mr. Biden’s answer, which followed the script written by Gov. Mario M. Cuomo, was no surprise. Everyone knows that the Democratic position that seeks few or no restrictions on abortion rights is not in line with Catholic doctrine. Some bishops have attempted to put politicians who espouse it on “wafer watch”; Mr. Biden was recently warned by the bishop of the diocese of Colorado Springs that he “ought not to be receiving Communion.” Align public policy with Catholic teaching, or be persona non grata at the altar of grace.

Far less pressure has been applied to the point at which the Ryan approach differs from Catholic teaching. Mr. Ryan said he couldn’t “see how a person can separate their public life from their private life or from their faith,” and then narrated the transfixing power of that first ultrasound. So far, so Catholic. But then came the focus-group-tested political answer: the policy of a Romney-Ryan administration would be “to oppose abortion, with the exceptions for rape, incest, and life of the mother.”