2020 could be the perfect storm, with states rushing to prepare for mass vote-by-mail operations for the first time, dozens of last-minute changes to state election rules, tight races in several swing states, a strong likelihood of protracted vote-counting, and two candidates who are already ready to fight it out in court.

"Uncertainty breeds litigation," said Edward Foley, an election law expert who directs the election program at Ohio State University. The more the litigation and the greater the political will to win, the more likely cases will end up before the Supreme Court, he added.

What we're watching: The court could play a big role even if it doesn't end up with a big post-election case like Bush v. Gore. Election-related cases are already working their way up toward the high court.

Pennsylvania Republicans are asking the Supreme Court to review a ruling that gave voters an extra three days to return their ballots in the state, for example.

Even the court's inaction can have real-world consequences — in July, the justices declined to get involved in the dispute over restoring felons' voting rights in Florida. That left rules in place that make it harder for those people to register.

Between the lines: All of this tension is heightened by the vacancy on the court and the prospect that President Trump may be able to fill that seat before the election.

If the court were to hear a big election-related case without a ninth justice in place, there'd be at least the possibility of a 4-4 tie.

When that happens in normal cases, the ruling from the court below stands, but no precedent is set — the same case can come back to the Supreme Court for a proper decision later. But that would be an untenable situation for an election, and Chief Justice John Roberts would surely do everything in his power to avoid it.

A court with three Trump nominees ultimately deciding the fate of Trump's reelection could have dire implications for public trust in the court. But a ninth justice may not be the deciding vote.

Just a few months ago, the court blocked efforts to extend absentee voting in the Wisconsin primary. Between that ruling, the decision not to intervene in Florida and striking down the core of the Voting Rights Act in 2012, voting-rights advocates had a pretty hard time at the high court even with Justice Ruth Bader Ginsburg on the bench.

The bottom line: Some experts argue that the odds of a close enough race in a decisive state, with sufficient grounds to settle it through litigation, are still low.