Republicans have asked the Supreme Court to step into a dispute over the rules of next week's election in the all-important battleground of Pennsylvania.
The Republican National Committee is asking the Supreme Court to stop the counting of provisional ballots from voters who return invalid mail-in ballots.
The state's election code says that provisional ballots "shall not be counted" from voters who cast mail-in ballots that are "timely received."
But the Pennsylvania Supreme Court ruled 4-3 to require the counting of provisional ballots from voters who cast mail-in ballots that are timely received but cannot be counted because of a defect such as a lack of a signature or secrecy envelope.
Republicans say the state court effectively created a new process to "cure" defective mail ballots that the state legislature never approved.
Without the Supreme Court's intervention, "tens of thousands" of ballots could be wrongly counted, Republicans argued, noting mail voting is well underway.
"Weeks after mail voting began in Pennsylvania—and less than two weeks before Election Day—a sharply divided 4-3 Pennsylvania Supreme Court departed from the plain terms of the Election Code to dramatically change the rules governing mail voting," they argued.
"It did so in the midst of the ongoing General Election in which millions of Pennsylvanians have already cast ballots for President, U.S. Senate, Congress, and scores of state and local offices."
The RNC is asking the court to either block the impacted provisional ballots or separate them from the official tally while the legal case continues.
"This case is of paramount public importance, potentially affecting tens of thousands of votes in a state which many anticipate could be decisive in control of the U.S. Senate or even the 2024 presidential election," lawyers for the Republicans wrote. "Whether that crucial election will be conducted under the rules set by the General Assembly or under the whims of the Pennsylvania Supreme Court is an important constitutional question meriting this court's immediate attention."
The request is part of a blitz of final pre-election litigation (although technically, the election has already started) to set the rules of the November elections. Virginia, in a separate dispute with the DOJ, has asked the Supreme Court to allow the state to remove 1600 self-declared non-citizens from the voter rolls.
Pennsylvania's 19 electoral votes make the state the biggest prize among the battlegrounds. President Trump has taken a narrow lead in Pennsylvania in recent polls.