As they look ahead to next year’s fight to control Congress in the midterms, Republicans and Democrats are scrambling across the country to revisit the congressional district lines that will shape political battles ahead.

Redistricting is usually performed only once a decade after the release of data from the U.S. Census. 

Texas Republicans, at the urging of President Donald Trump, passed a new map in August packing together Democratic voters in major urban and suburban areas and drawing new borders around Democratic seats to include more Texans who voted for Trump last year.

It set off a scramble capped by Tuesday’s ballot proposition in California, which would give Democrats a chance to pull even with new pickup opportunities, as both parties explore redrawing maps in states where they control the levers of power. 

Republicans make gains with new maps

As of Monday, four states have finished redrawing their congressional maps: Texas, Missouri, North Carolina, and Ohio.

Ohio, unlike the others, was required to redraw its congressional map because of state rules. A commission passed a “compromise” map that favors Republicans but keeps districts competitive for Democrats.

Analysts believe that Republicans stand to gain up to nine seats in these redrawn maps as state legislatures redrew five seats in Texas to favor Republicans, one in both North Carolina and Missouri, and two in Ohio.

Democrats put hope in California

But Democrats are holding out to pass a new map in California to cancel out Texas.

Voters there are heading to the polls to vote on Proposition 50, in which would adopt a new congressional map that redraws five districts to be more Democratic-leaning. Supporters of the initiative — and the ballot text itself — say it will counteract how Texas redrew its map.

Other states on the radar

A few other states are in the process of redrawing maps.

Utah legislators recently passed a new map after a court ruled against its current one; it is currently undergoing legal review. Democrats have been cautiously optimistic that one or two of the seats could become more competitive.

Indiana’s Republican-controlled state legislature is set to start considering mid-decade redistricting in a special session, while Virginia’s Democratic-controlled legislature is taking steps to allow it to consider a new map.

Other Republican-leaning states such as Florida, Nebraska, Louisiana, and Kansas, and Democratic-leaning states such as Maryland and Illinois, have mulled redrawing maps.

How this changes the battle for the U.S. House

There are 435 seats in the U.S. House. As of Monday, Republicans hold 219 seats to Democrats’ 213 with three vacancies.

With all seats filled, Democrats would need to net three seats in order to flip the House. 

Even though both parties were already eyeing seats they could pick up or flip since 2024’s House races, mid-decade redistricting means both parties have to rethink what seats remain competitive and if redistricting shrinks the battlefield of competitive seats.

For instance, in the 2024 elections for the U.S. House of Representatives, 13 Democratic candidates won in districts that Republican presidential candidate Donald Trump won, while three Republican candidates won in districts that Democratic candidate for president Kamala Harris won, according to an analysis by the Center for Politics at the University of Virginia.

Of those districts, four of them — Texas’ 28th and 34th, North Carolina’s 1st, and Ohio’s 9th — are Democratic-held districts won by Trump that the new maps have made more Republican-leaning.

That means at least four seats that both Republicans and Democrats would have a good shot at flipping have been redrawn to lean more towards Republicans.

A Republican strategist working on U.S. House races told ABC News that Texas appears to present Republicans a good opportunity for picking up seats, and that Republicans are optimistic about being able to pick up the newly redrawn seats in Missouri and North Carolina.

The National Republican Congressional Committee, the campaign arm of House Republicans, said in September that it would add three Democratic-held districts in Texas to the group’s “target list”.

But Democrats aren’t giving up.

Will Van Nuys, the deputy executive director of the Democratic Congressional Campaign Committee, House Democrats’ campaign arm, told ABC News “We’re still very actively engaged with our frontliners, whether it’s Henry Cueller, Vicente Gonzales in [Texas congressional districts] 28 and 34, whether it’s Don Davis in North Carolina or our offensive target in Texas-15 — that’s piece one,” he said. 

“I think piece two, in terms of come this time next year how it impacts the overall map — it’s a little premature to say because I think right now what you’re seeing is a lot of momentum coming towards the Democratic side.”

The Supreme Court could scramble the map further

An incoming ruling from the U.S. Supreme Court could further scramble the battle map for the midterms, depending on when a ruling comes down.

The court is considering a case that could determine whether Louisiana and many other states may have to redraw their maps in a race-blind manner. A decision is expected by the end of June 2026 when the court’s term ends.

Democratic-aligned groups have estimated that Republican-controlled legislatures could then redraw at least 19 Democratic-held seats across southern states.

ABC News’ Devin Dwyer and Benjamin Siegel contributed to this report.