Legal battles over redistricting in nearly a half-dozen states could leave operatives from both parties scrambling to understand a new political landscape in the months leading up to next year’s primary and general-election contests.

The biggest domino in that fight will fall by the end of June, when the Supreme Court is expected to announce whether it is constitutional for an independent redistricting commission to draw Arizona’s congressional map. If the court deems the map unconstitutional, it would upend Arizona’s district lines, and affect other states that also utilize independent redistricting commissions.

To be sure, it’s unlikely any of the changes would affect the balance of power in the House, where Democrats must net 30 seats to win a majority.

But a mid-decade redraw would create plenty of uncertainty — leaving members of Congress, potential candidates and party operatives in limbo as state legislatures work to draw new lines based on the 2010 census.

“There could be some considerable changes in some states, but when we look at the overall political environment, we likely would not see a huge effect from redistricting on the party’s fortunes in the 2016 election,” said Michael McDonald, an expert on redistricting who is an associate professor of political science at the University of Florida.

Here are the redistricting battles that could affect 2016:

Arizona: In March, the Supreme Court heard a case which argued the independent redistricting commission that drew the state’s congressional lines in the 2012 cycle violated the Elections Clause of the Constitution.

That clause states, “the Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof.”

If the court rules the definition of legislature refers just to the elected legislative body, that would invalidate Arizona’s map, as well as any other congressional map drawn without input or a signoff from a state legislature.

In Arizona, the Republican-held state Legislature would then have the power to redraw district lines. The Legislature would likely make the districts less favorable to Democrats — who currently hold four of the state’s nine seats.

California: Like Arizona, California’s congressional map was drawn by an independent redistricting commission — a process passed by ballot referenda in 2010.

If the Supreme Court tosses Arizona’s map based on the Elections Clause, California’s congressional districts would also be invalidated.

With a large majority in the state Legislature, as well as a Democratic governor, Democrats could gain seats in the 53-member delegation.

Democratic operatives say the redraw would allow their party to add more Democratic voters to competitive districts they already hold, effectively shutting out Republicans from playing in contests in the state.

Besides Arizona and California, three other states utilize independent commissions, but they aren’t expected to be affected by the ruling.

Florida: A redistricting battle has been raging in Florida since the 2014 cycle, when a judge ruled two of the Sunshine State’s 27 House districts did not adhere to the state constitution’s Fair District Amendment because they were not compact and also favored the GOP.

The state Legislature redrew the lines, and a judge deemed them permissible — ruling they should be used for the 2016 cycle.

But Florida Democrats again appealed the map, which would have minimal effects on party breakdowns in the affected seats. The state Supreme Court heard arguments in the case in March, and a decision is expected in the coming months.

North Carolina: In May, the U.S. Supreme Court ordered state judges to re-evaluate the Tar Heel State’s congressional map to determine whether the state legislature relied too heavily on race to draw the congressional map during the 2012 cycle.

The court pointed to its ruling in an Alabama redistricting case, which focused on whether too many black voters were packed into one district.

Fearing the state court would not rule quickly enough to have new district lines apply to the 2016 elections, opponents of the current map filed a second federal lawsuit last month in hopes of expediting the process.

Most likely to change if the plan is invalidated is the 12th District, a majority-minority district that runs along the Interstate 85 corridor from Winston-Salem and Greensboro to Charlotte.

Virginia: Last week, a panel of federal judges invalidated Virginia’s congressional map, ordering the state legislature to draw a new one by Sept. 1.

The court ruled the legislature packed too many black voters into Democratic Rep. Bobby Scott’s 3rd District, a violation of the Voting Rights Act.

In Virginia, Republicans control the state legislature, but Democratic Gov. Terry McAuliffe could veto a map Democrats deem unfair to the party.

In order to comply with the Voting Rights Act, operatives say GOP Rep. Randy J. Forbes’ 4th District could become the second majority-black district in the state — making it too challenging for Forbes to hold. More Democratic-friendly voters could also be added to GOP Rep. Scott Rigell’s Virginia Beach-based 2nd District, making it a more favorable seat for Democrats, though not a certain pick-up.

Virginia GOP Rep. Bob Goodlatte told The Richmond Times-Dispatch he expects Republicans will appeal the ruling to the Supreme Court.

Correction 11:53 a.m.

A previous version of this article misstated the number of Arizona House seats held by Democrats.

Related:

Both Parties Monitoring Impact of Arizona Redistricting Case

Court Tosses Virginia Congressional Map

Roll Call Race Ratings Map: Ratings for Every House and Senate Race in 2016

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