HARRISBURG, Pa. (AP) — Abortion rights, suddenly a potent political force in the aftermath of the U.S. Supreme Court's decision to leave such matters to the states, have found an unlikely champion in swing state Pennsylvania.

Sen. Bob Casey, who will appear on the November ballot beneath President Joe Biden as the Democrats both seek reelection, has begun doing something he's never done before: attacking an opponent over abortion rights.

The senator, who once called himself a “pro-life Democrat,” accuses Republican challenger David McCormick in a new TV ad of wanting to “make abortion illegal even in cases of rape and incest” — a characterization McCormick says is wrong.

Speaking to an online gathering of the progressive women’s advocacy group Red Wine & Blue earlier this month, Casey warned that electing a Republican president and a new Republican Senate majority could result in bans on the abortion pill and contraception, even in Democratic-controlled states — or purple states like Pennsylvania — where abortion remains legal.

“You could have blue-state impact whether it’s a blue-state ban that affects contraception or whether it’s a blue-state ban when it comes to abortion because of mifepristone,” Casey said.

That's quite a reframing for Casey, who like his father and Biden comes from an Irish Catholic family in Scranton. His father, who was a two-term governor of Pennsylvania, opposed abortion rights and signed legislation restricting abortion that spawned the landmark 1992 case Planned Parenthood v. Casey.

Sen. Casey, whose race is seen as crucial to Democrats' effort to defend their razor-thin Senate majority, says the Supreme Court's decision to strip women’s constitutional protections for abortion changed everything in the abortion debate and prompted a “pro-life Democrat” to support access to abortion.

Casey has suggested that “pro-life” never meant a complete ban on abortion without exception, at least to him. After the court's forthcoming decision had been leaked, Casey supported Democrats' legislation to keep abortion legal to the Roe v. Wade standard of barring abortion only after viability, around 24 weeks.

“Everyone in the Senate had a choice to make,” Casey told The Associated Press. “You had to decide, basically, whether you’d support banning abortion or not. And that was a choice you had to make. And the choice was also a choice about legislation. ... And I decided that I would support advancing that bill and thereby not being in the ban-abortion column.”

He had broken with Democrats in the past in supporting bills to ban abortions after 20 weeks and to block federal funding for abortion.

But he also had emphasized reducing abortions through services that prevent unwanted pregnancies and help pregnant women and young mothers, a reason he has given for backing federal funding for Planned Parenthood.

When the court overturned Roe v. Wade, Casey slammed it as ripping away a constitutional right and a dangerous decision that wouldn’t stop abortions but would put women’s lives at risk.

Democrats have been happy to embrace Casey’s recalibrated position.

“I don’t believe he ever wanted those (pro-life) beliefs to ever stand in the way of access to abortion, and now his position matters more than it did just two years ago,” said Brittany Crampsie, a Democratic strategist.

Mary Ziegler, a law professor at the University of California, Davis, who studies the history and politics of the abortion debate, said she thinks Casey had begun drifting from the anti-abortion movement well before the court overturned Roe v. Wade.

He was probably both pulled by a Democratic Party becoming more supportive of abortion rights and pushed by an anti-abortion movement becoming more aligned with Republicans and Christian conservatives, Ziegler said.

“If you take politics out of it, it’s possible that Casey has one of those purple positions on abortion that doesn't tend to track with what either movement is doing," Ziegler said.

Many Americans hold middle-of-the-road beliefs on abortion, Ziegler said, and Casey’s stance isn’t out of step with many lay Catholics. According to Pew Research Center surveys, 56% of U.S. Catholics say abortion should be legal in all or most cases.

Politically speaking, abortion rights has been a winner on the ballot since the court decision, even in red states such as Ohio, Kansas and Kentucky, where the outcomes favored keeping abortion access legal.

McCormick attacks Casey from the right. He accuses Casey of wanting to allow abortion “up until the moment of birth,” a refrain Republicans are using to attack Democrats' legislation, which allows an exception for abortions after fetal viability in extremely rare situations when a doctor determines the life or health of the mother is at risk.

Democrats say doctors — and not the government — should be making such decisions.

Meanwhile, McCormick says he opposes abortion, with three exceptions — rape, incest and to save the life of the mother — and not just one exception, as Casey contends. McCormick also says he wouldn’t vote for a federal abortion ban.

Casey, now in his eighth statewide campaign, has never previously wielded abortion rights as a weapon. He has been on defense, however.

In the 2002 Democratic primary for governor, Casey told a radio interviewer that he favored one exception, to save the life of the mother. But, he said, if the Supreme Court were to overturn Roe v. Wade then he, if elected governor, would sign legislation with all three exceptions, including rape and incest, “and it would have the effect of reducing the number of abortions in the state.”

Casey ultimately lost to Ed Rendell, who received support from the National Abortion and Reproductive Rights Action League, which ran ads against Casey because of his opposition to abortion rights.

In Senate races, Casey’s Republican opponents have tried to poke holes in his “pro-life" bona fides by pointing out that he opposed proposals to halt federal payments to Planned Parenthood.

Casey in 2006 was first recruited by national Democrats to run when he still wore the label of “pro-life Democrat.” He hasn’t faced a serious primary challenger in his four campaigns for the Senate.

Republicans frame his evolution on the issue as pure politics. They say he changed his position to survive the party’s leftward drift and never truly opposed abortion, like his father did.

“I don’t know how you go from defending life to the ad he’s running against Dave McCormick,” said Matt Beynon, a Republican strategist who worked on Lou Barletta’s losing campaign against Casey in 2018.

Democratic strategists insist that Casey’s evolution is natural and reflects a generational shift in which abortion is discussed alongside health care and contraception.

Christine Jacobs, who founded an organization to help elect Democratic women to Pennsylvania's Legislature, said Casey has spent years of thinking about it and talking about it with his staff.

Still, Democratic strategists are stumped by the question of whether Casey could have been the party’s unquestioned nominee in 2024 had he supported a ban when the party’s activists were mobilizing over abortion rights.

It’s an academic question now. But Jacobs — who, like Casey, grew up Catholic — thinks there would have been sufficient outrage.

“I think he would have had to pull out,” Jacobs said. “At least, I’d like to think that.”