WASHINGTON — When the Sandy Hook school shooting rocked the country, Pennsylvania Sen. Bob Casey changed his longtime stance on the Second Amendment, becoming a fierce advocate for stricter gun laws.

When a Supreme Court decision neared that would make same-sex marriage legal nationwide, Casey embraced the shift, abandoning his previous objections.

And when President Joe Biden took office early last year, Casey softened his stand on the Senate filibuster, suggesting he’d be open to changing the rule if it helped Democrats turn big, progressive ambitions into reality.

But as Casey has followed his party’s leftward trajectory over the past decade, one key issue still set him apart from most Democrats: abortion. Casey is one of the few major Democrats left who describes himself as “pro-life.”

On Tuesday, that rare break from his party put a glaring spotlight on Casey, as a draft Supreme Court opinion signals the end of nationwide abortion access, and pointed toward a future of intense legislative conflict to reset the terms of one of the country’s most divisive issues.

That fight could quickly put Casey in an awkward position. As most of his party reacted with fury, fellow Democrats urged a vote to codify Roe v. Wade, the abortion-rights decision the Supreme Court appears poised to overturn, while conservatives considered forcing a vote on nationwide abortion restrictions if they take control of the chamber.

Either could force Casey to take a clear, unambiguous stand that could shape one of the country’s most significant debates. His balancing act was starkly illustrated by his relative silence Tuesday as news of the impending decision rocked the Capitol and sparked protests across the street at the Supreme Court.

The normally amiable senator arrived to Senate votes, and left, with his cell phone pressed to his ear, twice refusing to acknowledge reporters who tried to ask his thoughts on the decision. When nearly all of his Democratic colleagues took to the Capitol steps to denounce the potential ruling, Casey was one of the few absent.

He instead issued a statement that raised concerns about the pending decision, without addressing the question of whether to write abortion rights into law, or to institute sharp nationwide restrictions.

“If this draft opinion becomes the final opinion of the Court, I have serious concerns about what overturning almost 50 years of legal precedent will mean for women in states passing near or total bans on abortion,” Casey said. “Congress should be working to reduce the number of abortions and unintended pregnancies and doing much more to support women and families.”

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Casey’s name is inextricably linked with the country’s abortion fights.

His namesake father, former Pennsylvania Gov. Bob Casey Sr., signed the abortion restrictions that were upheld in the landmark Planned Parenthood v. Casey Supreme Court decision in 1992. In large part because of that fight, the Casey name still conjures up sepia-toned visions of moderate Democratic politics for some.

And as the younger Casey became more and more aligned with his party on other flash points, his stand on abortion provided a distinguishing characteristic that, on one issue at least, set him apart from other Democrats in a competitive swing state.

But he has long walked a fine line on abortion. At times he has voted in favor of restrictions, such as a proposed ban after 20 weeks in 2018, but he has also supported funding for Planned Parenthood and other steps that, he argues, provide crucial health care and planning that can reduce the need for abortions.

He has opposed more drastic steps, like a near-total ban passed in Alabama in 2019, and has earned mostly positive marks from Planned Parenthood and NARAL Pro-Choice America, the latter of which gave him a 72% rating in 2020.

In February, Casey voted to allow formal Senate debate on the Women’s Health Protection Act, a bill to codify abortion rights law. That put him in line with fellow Democrats, but it was a procedural step, and his statement at the time left it unclear if he supported the underlying goal.

“I think it’s clear to most people that the description of pro-life Democrat is accurate. I’ve been very consistent,” Casey told Politico in 2018. “I try to support policies that help women and children both before and after birth. Part of that is making sure you are honest about differences but also at the same time trying to focus on ways to reduce both the number of abortions and the number of unwanted pregnancies, and I think my record reflects that.”

Often, however, his votes on abortion proposals have been on symbolic steps that had little chance of becoming law, decreasing the attention and passion they drew. The underlying support for abortion, Roe v. Wade, was still in place.

Now, the country is preparing for a drastic rewrite of laws that have stood for decades, and sharp new restrictions on abortion rights in many states. And while it’s still likely that neither party will have the 60 votes required to immediately advance their abortion plans through the Senate, the new votes are likely to carry more weight as drastic state restrictions — and potentially outright bans — become reality.

One of the states that could see such rollbacks is Pennsylvania, should Republicans win the governor’s office this fall and keep hold of the legislature.

“It’s certainly complicated for Casey. It always has been, given his position on abortion, given his family history, given his dad’s prominent role in the history of Roe v. Wade,” said Chris Borick, a pollster at Muhlenberg College. “He’s had to find a fairly delicate position.”

But the fact that he didn’t take absolutist stands in either direction, Borick said, likely muted the blowback he received from either the left or the right.

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Already on Tuesday, cracks were showing in that dynamic as the stakes increased. Some progressives saw Casey’s muted reaction as insufficient.

While praising Casey on reproductive rights, Kadida Kenner, executive director of the New Pennsylvania Project and cochair of Why Courts Matter PA, said the senator needs to cast aside his personal views and focus on upholding a popular law that most Pennsylvanians support.

”We all have our personal Constitutions,” Kenner said, “but I also believe that Senator Casey can see this from the legal standpoint. [Roe] has been the law of the land for 50 years … and he needs to continue to honor the will of his constituency.”

But Casey’s nuanced argument that backing funding for groups like Planned Parenthood are, in fact, anti-abortion positions has earned him little love from conservative groups.

The Pro-Life Coalition of Pennsylvania labeled the senator “duplicitous.”

“His pattern has been, when he voted pro-life, his vote didn’t matter. But when his vote did matter, he marched to the pro-abortion side,” said Mike McMonagle, the group’s director.

He predicted that Casey would continue that march when it comes to the Roe decision.

”It would be harder for him to go any further,” he said.