CINCINNATI — A panel of federal judges ruled Friday that Ohio's congressional districts were unconstitutionally drawn by the Republicans for their political advantage, and it ordered a new map for the 2020 elections.

The ruling, if it stands, could prove an important victory for the Democrats, who are hoping redrawn boundaries will not only help them pick up House seats but also energize voters and boost turnout in this longtime battleground state. Republican officials said they would appeal.

The panel unanimously declared the current map an “unconstitutional partisan gerrymander,” saying the GOP-controlled Ohio Legislature put the Democrats at a disadvantage by packing lots of them into four districts and scattering the rest across the remaining 12.

“Democratic candidates must run a significantly longer distance to get to the same finish line,” the judges wrote in a 301-page ruling.

The Republicans hold a 12-4 advantage in Ohio's congressional delegation under the current map, which went into effect for the 2012 elections.

The Supreme Court is already considering a gerrymandering case that could lead to a major decision on how far politicians can go in drawing districts. It involves challenges to congressional maps in North Carolina, drawn by Republicans, and Maryland, created by Democrats.

Republican Attorney General Dave Yost said he will seek to stay the court order while appealing to the U.S. Supreme Court. He also said Ohioans have already approved mapmaking reforms that will be in effect for redistricting after the 2020 census.

The judges — two nominated by Democratic presidents, one by a Republican — ordered a proposed new map by June 14. T

Voters' rights and Democratic groups had sued Ohio Republican officials, saying redistricting after the 2010 census yielded a map that has produced an impenetrable GOP advantage.