Supreme Court Ruling Means We Probably Won't Know Who Won Pennsylvania Until Days After Election

And maybe a lot longer, since the Supreme Court left the door open to re-hearing a Republican-led challenge seeking to discard late-arriving absentee ballots.

Pennsylvania is the state most likely to decide next week's presidential election, but a Supreme Court ruling this week has all but guaranteed that we won't know who won the Keystone State's 20 electoral votes on Election Day.

The Supreme Court on Wednesday rejected a Republican effort to force Pennsylvania to discard mail-in ballots received after Election Day, but the high court left open the possibility of re-hearing the case after the election if those ballots could alter the outcome. Last month, the Pennsylvania Supreme Court ordered counties to accept and count ballots that arrive through November 6, three days after the election, even if those ballots don't contain postmarks showing when they were mailed.

If the election in Pennsylvania is close—and if the overall results hinge on who wins Pennsylvania—those late-arriving ballots are likely to end up being 2020's version of the infamous "hanging chads" that defined the 2000 presidential election in Florida.

In a statement announcing the court's decision on Wednesday (no formal opinions were issued), Justices Samuel Alito, Clarence Thomas, and Neil Gorsuch said that "it would be highly desirable to issue a ruling" on the Pennsylvania ballot rules before the election, but that the court decided "there is simply not enough time" to give the issue a proper hearing "at this late date."

Meanwhile, Pennsylvania's secretary of state issued new guidance to county-level election offices on Wednesday instructing officials to keep late-arriving ballots separate from absentee ballots that arrive before or during Election Day.

That should help avoid some of the potential chaos. But other issues are looming too.

Unlike most other states, Pennsylvania does not allow mailed-in ballots to be opened or counted before Election Day, which means election offices have not been able to get a head start on what's likely to be a record number of absentee ballots cast this year. Under state law, counties can begin counting those ballots at 7 a.m. on Election Day, but some counties have already decided they won't begin counting any absentee ballots until the day after the election, PennLive reports. In Cumberland County, a Republican-run suburban county near Harrisburg, that means at least 45,000 votes won't be counted the day of the election.

Statewide, there are expected to be more than 2 million mail-in ballots waiting to be counted. State officials maintain that the "overwhelming majority" of those votes will be counted by the Friday following Election Day, The Philadelphia Inquirer's Angela Couloumbis reports. Still, there's plenty of room for the results to shift in the days after the election. Keep in mind that President Donald Trump won Pennsylvania by less than 50,000 votes in 2016.

"We need to brace ourselves for a 'blue shift' in states like Pennsylvania," advises FiveThirtyEight's Geoffrey Skelley. "That is, states that primarily report Election Day results first could show Republicans with an initial lead on election night only to then shift toward Democrats as more mail ballots are counted."

In short, it looks like the best-case scenario in Pennsylvania is that a winner is announced before the end of next week. The worst-case scenario sees a Florida 2000–type mess and the election's outcome landing in front of the Supreme Court.

If that happens, newly minted Justice Amy Coney Barrett will be part of the decision-making process. She did not participate in this week's decision to punt the Pennsylvania ballot issue—or similar cases involving late-arriving mail-in ballots in North Carolina and Wisconsin—because she did not have time to fully review the cases. She did not recuse herself.

On Monday, Trump tweeted that states "must have final total on November 3rd."

In Pennsylvania—and probably in a few other places too—that is simply impossible.