The U.S. Supreme Court said Monday that it won’t hear several challenges to Pennsylvania’s 2020 election — including two appeals of the state’s mail-ballot deadline extension — denying a Republican attempt to severely limit courts’ ability to oversee how elections are run.

The decision not to hear the legal challenges brought by top Republican state lawmakers and the state GOP ends litigation that prevented Pennsylvania from counting 10,000 mail ballots that arrived in the three days after Election Day and had remained in legal limbo. But one final legal challenge to those ballots remains before the high court, and the Pennsylvania Department of State isn’t counting them until that case is resolved. If counted, they would likely extend President Joe Biden’s 80,000-vote victory in the state.

The decisions show how the campaign to challenge and undermine the election results by Donald Trump and his allies outlasted even his presidency, and are only now close to coming to an end after meeting near-universal defeat in state and federal courts.

The decisions also set back a Republican push to significantly shift the election law landscape by essentially shutting out courts from making changes to election procedures. The U.S. Constitution gives state legislatures the power to decide how elections are run, but that has long been understood to mean the normal legislative process, including sign-off from governors and judicial review of the law.

The question of court oversight and state legislative power remains unresolved, in what one expert called “a ticking time bomb.”

Justices Clarence Thomas, Samuel Alito, and Neil Gorsuch dissented, saying they would have heard the two mail-ballot deadline extension cases.

The court also decided not to hear a case brought by the Trump campaign that sought to overturn a number of Pennsylvania Supreme Court decisions, and a case brought by U.S. Rep. Mike Kelly (R., Pa.) and others that challenged the state’s mail voting law itself.

In a statement, Kelly called it “astounding” that the court won’t hear the case arguing that the state’s Act 77 law establishing no-excuse mail voting violated the state’s Constitution. He also called for a repeal of the mail voting system so it can be put before voters as a proposed constitutional amendment instead.

» READ MORE: 10,000 Pennsylvania votes are in limbo. They won’t change the outcome. They could still have a huge impact.

The ballot deadline cases stemmed from a September decision by the Pennsylvania Supreme Court to extend the state’s deadline by three days because of concerns about mail delivery delays.

State election law requires mail ballots to be received by 8 p.m. on Election Day. Responding to a request from the Pennsylvania secretary of state, the state Supreme Court ordered ballots to be counted if they were received by 5 p.m. Friday, Nov. 6, and postmarked by Election Day or lacked evidence of being sent afterward.

Republicans said that would invite fraud by allowing votes to be cast after Election Day. Republicans who control the state Senate quickly went to the U.S. Supreme Court to request a stay, as did the Republican Party of Pennsylvania.

The requests made essentially the same two arguments. First, they argued, the Pennsylvania Supreme Court was effectively allowing voting after Election Day, violating the federal law establishing one single Election Day. In addition, the Republicans said, the U.S. Constitution gives state legislatures the power to decide how elections are run. By extending the deadline in this election, they said, the state’s high court was unconstitutionally taking that power away from lawmakers.

In October, the U.S. Supreme Court split 4-4 on whether to step in and block the deadline extension, allowing it to stand. Republicans then filed their appeals, asking the court to take up the actual cases.

About 10,000 ballots arrived in that grace period. None were counted in the certified totals, pending resolution of the Supreme Court challenges.

The immediate impact of the court’s decision is that those post-Election Day ballots can now be counted, though the state is waiting for the final case. But the greater impact is in what didn’t happen: In refusing to hear the cases, the U.S. Supreme Court sidestepped an opportunity to rule on what’s known as the “independent state legislature” doctrine and decide the limitations of legislatures’ and courts’ power to decide election rules.

Because the U.S. Constitution gives state legislatures the power to decide how elections are run, an argument taken up by Republicans says courts don’t have much oversight, if any. In the case of the 2020 election, that would mean the Pennsylvania Supreme Court overstepped its boundaries when it extended the deadlines for mail ballots.

The opposing view — one that has largely been the norm — sees lawmakers’ power as part of the normal legislative process. By staying out of the fight right now, the U.S. Supreme Court left the question open for the future, said Josh Douglas, an election law professor at the University of Kentucky.

“The powers are what they were previously … until the U.S. Supreme Court says otherwise,” Douglas said. While some people, especially Democrats, may see Monday’s decision as a win because it avoided the possibility of a major decision, “legally we just don’t have a definitive answer either way,” he said.

» READ MORE: Fact-checking false claims about Pennsylvania’s presidential election by Trump and his allies

The Department of State and Democrats had argued the cases should be dismissed as moot, saying the election had been certified and there were too few late-arriving ballots to change the result of the presidential race.

Republicans said that made this election the perfect vehicle for answering the larger questions, since no immediate election would be at stake.

The three justices who would have heard the cases agreed.

“One wonders what this [c]ourt waits for,” Thomas wrote in his dissent. “We failed to settle this dispute before the election, and thus provide clear rules. Now we again fail to provide clear rules for future elections. The decision to leave election law hidden beneath a shroud of doubt is baffling. By doing nothing, we invite further confusion and erosion of voter confidence. Our fellow citizens deserve better and expect more of us.”

For now, the status quo remains.

“This ‘independent state legislature’ doctrine is a ticking time bomb,” wrote Rick Hasen, law and political science professor at University of California, Irvine, “and it is an issue the Court is going to have to resolve, because these issues will return.”