HANOVER TOWNSHIP, Pa. — Jan Downey, who calls herself “a Catholic Republican,” is so unhappy about the Supreme Court’s likely reversal of abortion rights that she is leaning toward voting for a Democrat for Pennsylvania governor this year.

“Absolutely,” she said. “On that issue alone.”

Linda Ward, also a Republican, said the state’s current law allowing abortion up to 24 weeks was “reasonable.”

But Ms. Ward said she would vote for a Republican for governor, even though all the leading candidates vowed to sign legislation sharply restricting abortion. She is disgusted with inflation, mask mandates and “woke philosophy,” she said.

“After what’s happened this past year, I will never vote for a Democrat,” said Ms. Ward, a retired church employee. “Never!”

Pennsylvania, one of a handful of states where abortion access hangs in the balance with midterm elections this year, is a test case of the political power of the issue in a post-Roe world, offering a look at whether it will motivate party bases or can be a wedge for suburban independents.

After a draft of a Supreme Court opinion that would end the constitutional guarantee of abortion rights was leaked last week, Republicans downplayed the issue, shifting attention instead to the leak itself and away from its substance. They also argued that voters’ attentions were fleeting, that abortion was hardly a silver bullet for Democratic apathy and that more pressing issues — inflation and President Biden’s unpopularity — had already cast the midterm die.

To Democrats, this time really is different.

“These are terrifying times,” said Nancy Patton Mills, chair of the Pennsylvania Democratic Party. “There were so many people that thought that this could never happen.”

If Roe v. Wade is overturned, the power to regulate abortion would return to the states. As many as 28 states are likely to ban or tightly restrict abortion, according to a New York Times analysis.

In four states with politically divided governments and elections for governor this year — Pennsylvania, Michigan, Wisconsin and Kansas — the issue is expected to be a fulcrum of campaigns. In Michigan and Wisconsin, which have anti-abortion laws on the books predating Roe, Democratic governors and attorneys general have vowed to block their implementation. Kansas voters face a referendum in August on codifying that the state constitution does not protect abortion.

Pennsylvania, which has a conservative Republican-led legislature and a term-limited Democratic governor, is the only one of the four states with an open seat for governor.

“The legislature is going to put a bill on the desk of the next governor to ban abortion,’’ said Josh Shapiro, a Democrat running unopposed for the party’s nomination for governor. “Every one of my opponents would sign it into law, and I would veto it.”

Mr. Shapiro, the state’s attorney general, has been primarily known for defeating multiple cases brought by supporters of Donald J. Trump claiming fraud after he lost Pennsylvania by 80,000 votes in 2020. When Mr. Shaprio began his campaign last year, he focused on voting rights, but he said in an interview last week that he expected the general election to become a referendum on abortion.

His campaign said it had its best day of fund-raising after the Supreme Court draft leaked last week.

He rejected the notion that voters, whose attention spans can be short, will absorb a major Supreme Court reversal and move on by the fall. “I’m going to be talking about rights — from voting rights to reproductive rights — until the polls close at 8 p.m. on Election Day,’’ Mr. Shapiro said. “People are very concerned about this. I expect that level of concern, of fear, of worry, of anger is going to continue.”

All four of the top Republicans heading into the primary on May 17 have said they favor strict abortion bans. Lou Barletta, a former congressman and one of two frontrunners in the race, has said he would sign “any bill that comes to my desk that would protect the life of the unborn.”

Another top candidate, Doug Mastriano, said in a recent debate that he was opposed to any exceptions — for rape, incest or the health of the mother — in an abortion ban. Mr. Mastriano, a state senator, has introduced a bill in Harrisburg to ban abortions after a “fetal heartbeat” is detected, at about six weeks of pregnancy. Another Republican bill would require death certificates and a burial or cremation after miscarriages or abortions.

Democrats are worried, in Pennsylvania and around the country, that their 2020 coalition lacks motivation this year after expelling Mr. Trump from the White House. The listlessness extends to Black, Latino and younger voters, as well as suburban swing voters. It was suburbanites, especially outside Philadelphia, who gave Mr. Biden his winning edge in the state.

Democratic operatives hope abortion will keep those independent voters — who have since swung against the president in polls — from defecting to Republicans.

“With Trump no longer aggravating suburban voters every week, Republicans were hoping to regain traction in the Philadelphia suburbs in 2022,” said J.J. Balaban, a Democratic strategist in the state. “The fall of Roe will make that less likely to happen.”Shavonnia Corbin-Johnson, political director of the State Democratic Party, said that the end of abortion access would “add to compounding racial disparities and maternal health” for minority communities, and that the party was planning to organize aggressively around the issue.

Soleil Hartwell, 19, who works in a big-box store near Bethlehem, is typical of voters who drop off in midterm elections after voting in presidential years. But Ms. Hartwell said she would vote this year to protect abortion rights. “I don’t have any kids, and I don’t plan on having any yet, but if I was in a situation that required me to, I should be able to” choose the fate of a pregnancy, she said.

Republicans are deeply skeptical that abortion can reanimate the Democratic base. “Their people are depressed,” said Rob Gleason, a former chair of the Pennsylvania Republican Party. “Nothing’s going to be able to save them this year.”Speaking from Philadelphia after a road trip from his home in western Pennsylvania, Mr. Gleason said: “I stopped on the turnpike and paid $5.40 a gallon for gas. That reminds me every time I fill up, I want a change.”

Pennsylvania’s large Roman Catholic population — about one in five adults — has afforded electoral space for a tradition of anti-abortion Democratic officials, including Senator Bob Casey Jr., and his father, Bob Casey Sr., who served as governor. A law that the senior Casey pushed through the legislature in the 1980s included some abortion restrictions, which was challenged in the 1992 Supreme Court case Planned Parenthood v. Casey. The court upheld most of the state’s restrictions, while affirming Roe v. Wade’s grant of a right to abortion. The leaked draft of the court’s opinion last week, written by Justice Samuel Alito, would overturn the Casey ruling along with Roe.

Still, support for abortion rights in Pennsylvania has gradually increased, according to polling by Franklin & Marshall College over more than a decade.

Last month, 31 percent of registered voters said abortion should be legal in all circumstances, up from 18 percent in 2009. Those calling for abortion to be illegal in all circumstances declined to 16 percent, from 22 percent in 2009. A broad middle group, 53 percent, said abortion should be legal under “certain circumstances.”

The issue had not ranked high among the state’s voters before the Supreme Court leak. In a Monmouth University poll last month, abortion was cited as one of Pennsylvania voters’ top two issues by just 5 percent of Democrats and 3 percent of Republicans. Inflation topped the concerns of voters in both parties.

In Hanover Township, outside Allentown, an affluent suburb in a onetime Republican enclave that has trended blue, Dave Savage and Vincent Milite, both center-right voters, were analyzing the abortion issue through the eyes of their adult daughters, while loading groceries outside a Wegmans supermarket.

Mr. Savage, 63, said that his 30-year-old daughter felt strongly that abortion should be legal, and that therefore it would be an important issue for him in November.

A retired municipal employee, Mr. Savage said he was an independent voter but had primarily voted Republican most of his life. Come November, he would not support a candidate for governor who opposed abortion rights, he said. “My position is, I don’t have a vagina so I have no skin in the game.”

Mr. Milite read aloud a text between his two daughters, abortion-rights supporters, in reaction to a Facebook post by a cousin who wrote sharply of her opposition to abortion after the Supreme Court leak.

“I unfollowed her immediately,” one of Mr. Milite’s daughters texted the other. “I would never have an abortion, but I don’t have the right to tell” others what to do, she wrote.

Mr. Milite, a supervisor in municipal government, said he supported his daughters. “I’m a Republican, but I’m a moderate Republican,” he said. “I’m a Republican because this county was always Republican.”

He said he was undecided about whom to support in this month’s primary. His vote in the general election also seemed up for grabs.

“What’s going to happen is, you’re going to lose a lot of Republican votes” over abortion, Mr. Milite predicted. “I think it’s going to hurt the Republican Party.”