Numerous redistricting challenges pending in courts

The U.S. Supreme Court is scheduled to hear arguments Wednesday on a lawsuit alleging partisan gerrymandering in the drawing of a Maryland congressional district. Eight years after the 2010 Census provided the basis for legislative redistricting, several other cases alleging unconstitutional gerrymandering in various states also are still working their way through the court system.

In Pennsylvania, a recent court ruling reshaped congressional districts for this year's elections. But many of the other cases could have a greater impact in the years to come. That's because they could set precedents that states must follow during the next round of redistricting after the 2020 Census.

Here's a look at some key redistricting cases ruled upon recently or still pending in courts:

WISCONSIN

Partisan breakdown: State Assembly — 63 Republicans, 35 Democrats, one vacancy.

The claim: Partisan gerrymandering.

The case: A federal court in November 2016 struck down Wisconsin's state Assembly districts enacted in 2011 by the Republican-led Legislature and Republican governor as an unconstitutional partisan gerrymander in violation of Democratic voters' rights to representation. The U.S. Supreme Court heard arguments in October 2017 and has yet to rule in the case. It could set a precedent for whether and how courts can determine if partisan gerrymandering is unconstitutional.

MARYLAND

Partisan breakdown: U.S. House — seven Democrats, one Republican.

The claim: Partisan gerrymandering.

The case: A federal lawsuit filed in 2013 by Republican voters alleges that the Democratic governor and Democratic-controlled Legislature unconstitutionally gerrymandered the 6th Congressional District in 2011 to dilute the voting power of Republicans. The district had been held by a 20-year Republican incumbent. It's since been held by a Democrat. The U.S. Supreme Court is to hear arguments Wednesday challenging a federal court's refusal last August to bar continued use of the redistricting plan. The lower court put the case on hold pending guidance from the Supreme Court.

TEXAS

Partisan breakdown: U.S. House — 25 Republicans, 11 Democrats. State Senate — 20 Republicans, 11 Democrats. State House — 94 Republicans, 56 Democrats.

The claim: Racial gerrymandering.

The case: U.S. and state House maps enacted in 2011 by the Republican governor and GOP-led Legislature were tossed out in 2012 by a federal court, which produced new interim maps. Those maps were permanently adopted by the Legislature and governor in 2013. But last year, the federal court ruled that some districts were racially gerrymandered to weaken the electoral power of growing minority populations. The U.S. Supreme Court has blocked lower court orders to redraw two congressional districts and nine state House districts for the 2018 elections and is scheduled to hear arguments April 24 on an appeal of the lower court rulings.

PENNSYLVANIA

Partisan breakdown: U.S. House — 12 Republicans, six Democrats if Democrat Conor Lamb's lead holds up in a March 13 special election to replace resigned Republican Rep. Tim Murphy.

The claim: Partisan gerrymandering.

The case: The Pennsylvania Supreme Court ruled in January that the U.S. House districts enacted in 2011 by a Republican governor and GOP-led Legislature were an unconstitutional partisan gerrymander favoring Republicans. The Democratic-led court in February imposed new district boundaries that analysts said could boost Democrats' electoral prospects. The U.S. Supreme Court and a lower federal court both declined March 19 to halt or overturn the use of the new districts in this year's elections.

NORTH CAROLINA

Partisan breakdown: U.S. House — 10 Republicans, three Democrats. State Senate — 35 Republicans, 15 Democrats. State House — 75 Republicans, 45 Democrats.

The claims: Racial and partisan gerrymandering.

The cases: The U.S. Supreme Court in January temporarily blocked a lower court's order for state lawmakers to again redraw North Carolina's congressional districts, pending an appeal of the panel's ruling. That ruling held that the Republican-led legislature engaged in unconstitutional partisan gerrymandering when it redrew districts in 2016. Lawmakers were redrawing districts because a different federal judicial panel had stuck down the Legislature's 2011 redistricting plan as an unconstitutional racial gerrymander. Separately, the U.S. Supreme Court in February temporarily blocked portions of the lower court's decision redrawing state legislative districts. That was pending an appeal of the panel's ruling that the Republican-led legislature's 2017 redistricting plan violated the state constitution and contained racial biases left over from the maps it originally approved in 2011.

VIRGINIA

Partisan breakdown: U.S. House — seven Republicans, four Democrats. State Senate — 21 Republicans, 19 Democrats. State House — 51 Republicans, 49 Democrats.

The claim: Racial gerrymandering.

The cases: The U.S. Supreme Court last year ordered a lower court to reconsider previously rejected claims that a Republican-led Legislature and governor unconstitutionally diluted black voting strength in the state. The claim was that Republicans did so by packing a high percentage of black voters into 11 state House districts under a 2011 redistricting plan. That case is still pending. A separate case pending before the state Supreme Court alleges that 11 state House and Senate districts are not compact enough. In yet another case, a federal court in 2016 redrew congressional districts after ruling that black voters had been illegally packed into a particular district to diminish their voting strength elsewhere.

GEORGIA

Partisan breakdown: State House — 116 Republicans, 64 Democrats.

The claim: Racial gerrymandering.

The case: A federal lawsuit filed last April alleges that two state House districts were unconstitutionally gerrymandered by the Republican-led Legislature in 2015 to increase the percentage of white voters and decrease the percentage of black voters. Both Republican incumbents were re-elected over black Democratic challengers in 2016. Pre-trial motions to grant a preliminary injunction against continued use of the districts are under consideration.

MICHIGAN

Partisan breakdown: U.S. House — nine Republicans, four Democrats, one vacancy. State Senate — 27 Republicans, 11 Democrats. State House — 63 Republicans, 46 Democrats, one vacancy.

The claim: Partisan gerrymandering.

The case: A federal lawsuit filed in December by Democratic voters alleges the U.S. House and state legislative districts enacted in 2011 by a Republican governor and Republican-led Legislature are unconstitutionally gerrymandered to dilute the voting power of Democrats. Republicans have controlled the state legislative and congressional delegations since then. Pre-trial motions to dismiss the lawsuit are under consideration.

ALABAMA

Partisan breakdown: State Senate — 26 Republicans, seven Democrats, one independent, one vacancy. State House — 70 Republicans, 32 Democrats, three vacancies.

The claim: Racial gerrymandering.

The case: Most state House and Senate candidates will be running for office under new districts this year. That's the result of a lawsuit alleging that maps approved in 2012 by the Republican-controlled Legislature packed too many black voters into certain districts. The U.S. Supreme Court in 2015 ordered the maps to be reconsidered by a lower court, which struck down a dozen districts last year. The Legislature then redrew 25 of the 35 Senate seats and 70 of the 105 House seats, reducing racial polarization in most districts. The court dismissed a challenge to the new maps last October.