Pennsylvania Republicans will ask the U.S. Supreme Court to decide the legality of allowing voters to return mail ballots up to three days after Election Day, potentially queuing up the first partisan election case for the court to consider since the death of Justice Ruth Bader Ginsburg.

The state’s top four legislative Republicans indicated in a court filing that they plan to ask the Supreme Court for an emergency stay to block a state court’s decision from taking effect in time for the fall election. The Republicans filed a stay request with the Pennsylvania Supreme Court on Tuesday, writing that they planned to appeal to the country’s highest court, as well.

It remains to be seen how the Supreme Court will handle the appeal. The death of Ginsburg, heralded by liberals as a powerful champion for voting rights, has brought new uncertainty to the battles over election rules in 2020 playing out across the country.

Last week, the Pennsylvania Supreme Court ruled in Democrats’ favor on a number of mail-voting rules, permitting voters to turn in ballots via drop box in addition to using the U.S. Postal Service; allowing ballots to be returned up to three days after Election Day; and blocking a Republican effort to allow partisan poll watchers to be stationed in counties where they do not live.

Republicans are asking the Supreme Court to weigh in only on the state court’s ruling pushing back the deadline for mail ballots to arrive. The state court ruled that such ballots must be counted if they are postmarked by Nov. 3 — and even if they are not, “unless a preponderance of the evidence” shows that the ballots were mailed after Election Day.

Republicans argued that the ruling allows ballots to be counted even if they are cast after Election Day. “The Elections Clause of the United States Constitution vests the authority to regulate the times, places, and manner, of federal elections to Pennsylvania’s General Assembly, subject only to alteration by Congress, not this Court,” the Republicans wrote to the state court on Tuesday. The Hill first reported the filing. Democrats said they will oppose the GOP’s efforts to delay implementation of the new ballot deadline.

President Trump won Pennsylvania over Democratic nominee Hillary Clinton in 2016 with a margin of just 44,000 votes, or less than one percentage point.

Once the Republicans file their request for an emergency stay with the U.S. Supreme Court, it will land on the desk of Justice Samuel A. Alito Jr., who oversees the Philadelphia-based U.S. Court of Appeals for the 3rd Circuit. The entire court can weigh in on the decision whether to grant the stay.

Without Ginsburg, the court has just eight justices headed into Election Day, as it had four years ago, but this time with a more conservative tilt — five justices nominated by Republican presidents and three nominated by Democrats. Trump has said he plans to nominate someone to the open seat by the end of the week.

Separately, Republicans returned to a lower federal court Tuesday seeking to declare some of the other provisions of the state court decision unconstitutional, including allowing election officials to install drop boxes for voters and prohibiting out-of-county individuals from serving as partisan poll watchers.