Will abortion ruling boost Democrats? For voters, it’s complicated.

For activists at both ends of the spectrum, abortion is a pivotal issue. A decision to overturn Roe and let states decide would test the extent to which it motivates average voters.

Sitting around a foldout table in a dimly lit union hall, Susan DeRose deftly folds sample ballots into thirds, building a sloping pile in front of Amber Stern and Ann Szlivko, who try to keep pace as they put the ballots into clear plastic baggies along with pamphlets for Democratic candidates. 

As volunteers with Pennsylvania’s Lehigh Valley for...