Trump may sound moderate on abortion. The groups setting his agenda definitely aren’t.

As president, Trump delivered for anti-abortion voters in the biggest way possible by appointing the three Supreme Court justices who cast the deciding votes to overturn Roe v. Wade.

This year, however, the man who once proudly proclaimed himself “the most pro-life president in American history” has been wishy-washy on the subject as he campaigns, no doubt aware that pro-abortion-rights candidates and measures have been consistently winning since Roe fell.

In March, Trump voiced his potential support for a 15-week federal ban on the procedure. But on Monday, he said...