On June 24, 2022, the high court -- with a super-conservative majority built under Trump's presidency -- overturned the historic ruling in Roe v. Wade that had protected abortion rights, placing the issue in the hands of the states.
That same day, a handful of US states banned abortions, forcing clinics to close in haste or move to more welcoming places.
The nation, already politically polarized, is now split between the states that have banned or significantly restricted access to the procedure -- and the states that have adopted new protections for a woman's right to terminate a pregnancy.
The Supreme Court's decision sent political shockwaves across the country, and had repercussions -- since the ruling, conservatives have lost nearly every referendum or vote revolving around abortion access.
And some of those losses came in states that have recently shifted solidly to the right, such as Ohio, Alabama and Kansas.
Kamala Harris takes the baton
Since Roe was overturned, "the abortion rights movement discovered that Americans care more about abortion rights than may have been anticipated," said Mary Ziegler, a professor at the University of California, Davis law school.
"And so they are trying to capitalize on that in ballot initiative fights that have gone mostly the way of the abortion rights movement," she told AFP.
Democrats are making the most of the moment, hoping to win some crucial support from women and young voters.
Biden, a practicing Catholic who was long vexed by the issue, has become a champion of abortion rights and made it a defining part of his reelection bid, winning the backing of several family planning organizations.
Vice President Kamala Harris, the first woman in the job, has crisscrossed the country for months to mobilize her party faithful.
The 59-year-old Harris in March became the first vice president to visit a clinic performing abortions, in Minnesota.
On Monday, she will hold an event in Arizona -- a state seen as a crucial battleground in the November presidential election, and one where the supreme court said a Civil War-era rule banning abortion was valid.
Democratic Governor Katie Hobbs later signed a repeal of the 1864 law.
Across the country, Democrats have also encouraged the organization of mini-referendums on abortion in key states, so that they will coincide with the presidential vote -- and hopefully motivate unenthused voters to cast ballots.
Trump deliberately vague
Democrats are right to be confident in their reasoning, if an avalanche of opinion polls are correct.
According to a Fox News poll published Wednesday, 47 percent of voters consider abortion to be "extremely important" in how they decide between Biden and Trump.
The presumptive Republican candidate, who often mentions that he nominated three Supreme Court justices who helped to overturn Roe v. Wade, has lately been decidedly vague on the issue of abortion.
"You must follow your heart on this issue but remember, you must also win elections," Trump said in a video message in early April.
He has not campaigned on any promise to make abortion illegal with federal legislation, as the religious right has lobbied him to do.
"The best you can do if your position is unpopular is to not clarify your position," Ziegler says.
Biden, whose approval rating is less than stellar, will almost certainly attack Trump on the issue when the two take the stage Thursday for their first debate in 2024.
