Shortly after Ruth Bader Ginsburg’s death, Sen. Ted Cruz (R-Tex.) made the case for Republicans doing what they refused to in 2016: fill a Supreme Court vacancy in a presidential election year.

“We cannot have Election Day come and go with a 4-4 court,” Cruz told Fox News’s Sean Hannity, adding: “I think we risk a constitutional crisis if we do not have a nine-justice Supreme Court, particularly when there is such a risk of a contested election.”

It bears noting that Republicans weren’t nearly so concerned about such a prospect in 2016; in fact, Cruz himself said back then that a 4-4 court would be no big deal. But the thrust of his recent comments was telling. Republicans would very much like to have a GOP-appointed justice to help resolve any disputes arising about the 2020 election. President Trump has also said as much.

That prospect already loomed large, given all the legal wrangling over increased mail-in ballots during the coronavirus pandemic. Now it looms even larger.

The Supreme Court on Monday did indeed deadlock on a key voting issue in a key state. In a 4-to-4 split, it failed to reach an agreement on whether to stop Pennsylvania from counting mail-in ballots received after Election Day (but postmarked by that day). The lack of a stay in the case was a win for Democrats, because it keeps in place the Pennsylvania state Supreme Court’s ruling that such ballots can be counted up to three days after Election Day. Republicans had sought to put that decision on hold — one of many GOP efforts to apply stricter rules to mail-in voting, which leans overwhelmingly Democratic right now.

But the ruling was also somewhat ominous for Democrats, in that it reinforces the impact Amy Coney Barrett’s ascension could have on the court, rather quickly.

Election law experts noted that the decision was notable for a couple reasons.

The first is how it was handed down. The justices didn’t explain their decision, meaning we don’t really know what they were thinking and what the source of the deadlock might have been. All we know is that the court’s four most conservative justices — Clarence Thomas, Samuel Alito, Neil M. Gorsuch and Brett M. Kavanaugh — all would have granted the stay, and that Chief Justice John G. Roberts Jr. joined the three most liberal justices in opposing it.

The second is that the deadlock occurred despite two weeks of negotiations. That suggests the justices genuinely tried to reach an agreement — and failed.

It’s impossible to say the court, as it’s currently constituted, might split 4-4 on any other specific case involving voting rights, but the failure to reach an agreement despite an apparent attempt to — and along such firm ideological lines — suggests it’s quite possible. And that means that Barrett could almost instantly become the swing vote on these issues if and when she’s confirmed. (The Judiciary Committee is set to vote on her nomination this week, with the full Senate scheduled to give its final sign-off next week). It’s even conceivable that she could have an impact on the Pennsylvania case, given that the decision was about a temporary halt and didn’t deal with the merits of the case.

The question from there is whether she would intervene. And it’s a complicated one.

During her confirmation hearing, Democrats repeatedly pressed Barrett on whether she would recuse herself from cases involving the 2020 election — fearing just such a scenario in which a new justice would effectively help the president who had just nominated her. Sen. Patrick J. Leahy (D-Vt.) noted that then-Michigan state Supreme Court Justice Joan Larsen and a colleague had in 2016 recused themselves from a case involving a potential recount of the state’s votes because they had been on Trump’s list of potential Supreme Court nominees.

Barrett, perhaps unsurprisingly, wouldn’t commit. She said she couldn’t “offer an opinion on recusal without short-circuiting” the usual process, which involves studying a specific case for potential conflicts and consulting with other justices. Barrett would say only that she would take the issue seriously.

“I promise you that if I were confirmed and if an election dispute arises — you know, both of which are ‘if’ — that I would very seriously undertake that process and I would consider every relevant factor,” Barrett said. “I can’t commit to you right now, for the reasons that we’ve talked about before, but I do assure you of my integrity, and I do assure you that I would take that question very seriously.”

There is quite simply nothing stopping Barrett from voting on such cases, though, if she decides she can and should. And she could reason that appointees of presidents often rule in cases involving those presidents.

But Barrett acknowledged during other parts of her testimony that recusal standards deal not just with actual conflicts of interest but also perceived ones. Providing a decisive vote that benefits the reelection of the president who had just nominated her — particularly after Trump repeatedly and baselessly suggested mail-in voting leads to massive fraud, even before nominating her — would certainly raise questions about that. Barrett said she has made no promises about how she might rule in specific cases, but Trump’s frequent commentary about mail-in voting makes no secret about how he would have wanted his nominee to rule in cases like Pennsylvania’s.

There are also potentially compelling reasons for Barrett to avoid becoming a decisive vote, even if she doesn’t necessarily think she must recuse. Chief among them is how much blowback it might invite. We’re already dealing with a situation in which Democrats are talking about “packing” the court by adding more justices — retaliation for the GOP’s 2016 blockade of Merrick Garland and its flip-flop on election-year nominees after Ginsburg’s death. Casting a key vote in an area on which Democrats repeatedly warned her against helping Trump would certainly raise tensions in that regard. For now, Barrett will make an effective 6-to-3 conservative majority on the court, but that majority wouldn’t last long if Democrats can pack the court (by winning back both the presidency and the Senate) and decide to do it.

There’s also the relevant issue of just how decisive such a case might be. Pennsylvania is a key state, clearly, but an NPR analysis recently showed that ballots received after the election date there accounted for just 1.07 percent of mail-in ballots during the 2020 presidential primaries. That a significant portion of mail-in ballots, to be sure, and could be relevant in an exceedingly close election, which Pennsylvania was in 2016 (decided by 0.7 points). But even then, it would require both those votes to be pivotal in the state and Pennsylvania’s electoral votes to be pivotal in the presidential race.

That doesn’t mean other cases might not be more pivotal, and it was only five presidential elections ago that the Supreme Court was effectively tasked with deciding an election based upon a narrow issue in one key state (Bush v. Gore and Florida). The bigger issue with Barrett is how she might rule in even bigger cases, if they’re presented to her and the race is close enough for them to matter.

Monday’s decision makes it more likely she is put on the hot seat almost immediately upon her confirmation.