WASHINGTON — A federal court said Friday that Ohio's congressional district map — drawn by the Republican-controlled state legislature — unconstitutionally discriminates against Democrats, and ordered the state to come up with a new plan for the 2020 election.

"We are convinced by the evidence that this partisan gerrymander was intentional," said a unanimous three-judge panel, giving the state until June 14 to submit a new map. The ruling came in a lawsuit filed by the League of Women Voters.

The ruling said the current district plan "unconstitutionally burdens associational rights by making it more difficult for voters and certain organizations to advance their aims, be they pro-Democratic or pro-democracy."

The court said the map, drawn for the 2012 election and used since, "dilutes the votes of Democratic voters by packing and cracking them into districts that are so skewed toward one party that the electoral outcome is predetermined." In each of the four elections under the 2012 plan, Republicans have won 12 of the state's 16 congressional districts, leaving the Democrats with the remaining four.

Packing means drawing district boundaries so that minority voters are crowded into as few districts as possible and spreading out or "cracking" them among the remaining districts, where they can never achieve a majority to elect the candidates of their choice.

"Today's ruling ensures that voters' voices will be restored," said Jen Miller, executive director of the League of Women Voters of Ohio.

Dave Yost, Ohio’s Republican attorney general, said the state will appeal Friday's decision and seek a stay in the meantime to prevent it from taking effect. He called the ruling "a fundamentally political act that has no basis whatsoever in the Constitution."

In recent years, courts in other states have been willing to rule against single-party dominance by declaring that maps for congressional or state legislative districts are unconstitutional partisan gerrymanders. Just last week, a federal court in Michigan said that state's Republican legislature must come up with a new plan for its congressional districts, declaring that the votes of Democrats were unconstitutionally diluted.

But the Supreme Court has yet to establish a test for determining when the essentially partisan act of drawing political boundaries becomes too political.

Confronted with similar challenges in the past, the justices concluded that it would be impossible for the courts to know when partisan gerrymandering crossed a constitutional line. In 2004, the court rejected a claim that a Pennsylvania gerrymander was too partisan, though Justice Anthony Kennedy indicated then that such a lawsuit might succeed if the right kind of proof came along. He has since left the court, replaced by the more conservative Brett Kavanaugh.

Two cases are pending before the high court, challenging congressional redistricting plans that locked in an advantage for Republicans in North Carolina and gave an extra seat to Democrats in Maryland. Those decisions are expected by late June.