“Women see this as ‘my autonomy,’ and there is no space for compromise in their minds on autonomy,” said Tresa Undem, a partner with the research firm PerryUndem who studies public opinion on the issue. “Honestly, Democratic candidates are catching up to Democratic voters who have been feeling this way for a few years.”

Few states have a political history as shaped by the subtleties of the abortion debate as Pennsylvania. It has been home to Democrats like the former governor Robert P. Casey, who defended the state’s restrictive abortion laws in the landmark Supreme Court case Planned Parenthood v. Casey, which reaffirmed Roe but also allowed states to set new limits. Today Pennsylvania is represented in the United States Senate by the former governor’s son, Bob Casey, who is one of only a handful of Democratic senators with a record of voting to limit abortion access.

The state is also home to one of the last Republican House members who supported abortion rights, Charlie Dent, the former congressman who represented the Lehigh Valley area until he retired in 2018. There are none today.

“They used to talk about the Catholic Democrat, or the Casey Democrat, who was pro-labor, pro-life, pro-gun,” Mr. Dent said in an interview. “But that doesn’t seem to be so common today. Or many of them have become Republicans.”

There are still some opponents of abortion barely hanging on as Democrats. “I’m really sad because I don’t want to be a Republican,” said Jeannie Wallace French of Pittsburgh, who has worked with groups like Feminists for Life, which oppose abortion but are less partisan than many mainstream groups. She was pregnant with twins when she said the doctors discovered one had a form of spina bifida and advised her to abort. She declined and the baby, a girl, died shortly after birth. But doctors were able to use her heart valves to save two other infants.

She worries that stories like hers are getting drowned out. “It has become so loud, going both ways,’’ she said. “And the divide is only getting bigger.”