The Supreme Court could throw a wrench into Virginia politics with a decision expected this month.

The state is holding primaries Tuesday, but under one seemingly longshot outcome in a case still to be decided, the justices could require revisions to about two dozen state House voting districts and, in theory, a new primary within months.

A district revision and revote before November's general election has the potential to be confusing and disruptive, and an additional cost.

Some candidates running for the Virginia House of Delegates could need to requalify for the ballot. Hundreds of thousands of voters might need to be told that the district they vote in to choose their state House member has changed for the second time in less than a year.

The court's decision could come as early as Monday. Supreme Court experts, however, say it's almost unthinkable that the justices' decision will change the districts and cause election drama.

"I just think it's so unlikely that the Supreme Court is going to mess with the districts at this point I would not be overly concerned," said Richard Hasen, an election law expert and professor at the University of California, Irvine.

If Hasen is right, that will mean the state carries on with a plan to have voters choose lawmakers to the 100-member House using a map seen as favorable to Democrats in the general election. The map has the potential to flip control of the chamber, where Republicans currently hold by an 51-49 edge. Regardless of what the Supreme Court decides, it will be the last time the map is used because it will need to be redrawn following the results of the 2020 census.

In two other cases still awaiting decision, one from Maryland and another from North Carolina, the Supreme Court is considering whether electoral districts can be too partisan.

The map that Virginia is using to choose state House members was approved earlier this year by a three-judge court . It replaced a map drawn by the Republican-controlled House in 2011, after the last census and used in four elections since. Democratic voters sued in 2014, accusing Republicans of packing black voters into certain districts to make surrounding districts whiter and more Republican. A court found the map improperly factored race into the drawing of some districts and invalidated it.

When lawmakers couldn't agree on a replacement, the court chose one from a series of proposals. As a result, about 425,000 Virginia voters were told their voting districts had changed, according to the nonpartisan Virginia Public Access Project.

But the House hasn't given up on trying to have the state use the old map, defending it in the Supreme Court. Even before the justices heard arguments in the case nearly three months ago , however, they allowed the state to go ahead with planning for Tuesday's election using the new, court-selected map. Having the state change course now would be surprising, experts said.

"The Supreme Court, for a number of years, has been mindful that it doesn't want last minute changes to elections," said Scott Keller, a lawyer in private practice who argued redistricting cases before the Supreme Court as Texas' solicitor general. Keller said the court "understands it needs to provide advance guidance so that voters know who they're voting for and which district they're voting in."

Parker Slaybaugh, a spokesman for state House Speaker Kirk Cox, declined to speculate on the timing or the outcome of a Supreme Court opinion.

"Regardless of what the electoral map looks like in 2019, Republicans are prepared to defend and expand our majority in the House," he said in a statement.

If the justices were to make a decision that ultimately resulted in a change to one or more districts, state and local election officials would have to scramble. Among the things that would need to happen: new candidate deadlines, new election notices and setting up polling machines and polling places, all while officials plan for November's election.

The court-drawn map altered 25 districts, two of which have contested Democratic primaries that residents are voting in Tuesday. But it's unclear how many contested primaries there would be if the state were to be told to use the old House district map, or something else.

Marc Elias, who argued in favor of the court-selected map at the Supreme Court, said what the justices have done in the case so far suggests that voters will use the new map in November. But, he said, nothing is final until there's a Supreme Court decision.

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Associated Press writer Alan Suderman in Richmond, Virginia, contributed to this report.