Democrats on Thursday seized on a Supreme Court decision they called a “green light” for partisan gerrymandering, pledging to redouble their efforts to win control of state governments, judicial appointments and the U.S. Senate.

In fundraising appeals and calls to action, Democratic politicians and aligned groups outlined a series of moves they said would become the next stage of the battle over political maps, largely drawn by Republican-controlled legislatures in the past decade, that have entrenched GOP control of elected offices.

“This decision is an insult to our democracy and yet another reason Democrats need to win in 2020 – not just the White House, but seats up and down the ballot across the country,” Democratic National Committee Chairman Tom Perez said in a statement.

Republicans, meanwhile, applauded the decision and called for vigilance against further efforts to use redistricting cases to chip away at GOP control.

“Democrats will double down on flipping state Supreme Courts and bring more lawsuits to be heard by friendly judges they helped to elect,” said Scott Walker, a former Wisconsin governor and the national finance chairman of the National Republican Redistricting Trust. “Today’s decision is a great victory for our Constitution. Now, more than ever, we need all Republicans to join us or we will find ourselves gerrymandered into perpetual minorities by liberal state supreme courts.”

Advocates say fighting gerrymandering is a nonpartisan issue. But Democrats have been vocal opponents of the tactic, which has been shown to have given Republicans clear advantages in recent elections.

In Thursday’s 5-4 ruling, the U.S. Supreme Court declined to intervene on challenges to maps drawn by Republicans in North Carolina and by Democrats in Maryland, saying that federal courts can’t arbitrate complaints that maps were drawn to favor one party over another.

The ruling also likely derails challenges to maps that were drawn by Republicans in Ohio and Michigan, where lawmakers have appealed lower-court orders to create new congressional districts before the 2020 election.

From the archives: The many ways to draw a gerrymander

But the Supreme Court did not preclude similar challenges from advancing in state courts. One such case, Common Cause v. Lewis in North Carolina, is scheduled to go to court July 15. The plaintiffs in that case have argued that the GOP-drawn lines in the Tar Heel State violate provisions in the state constitution.

“The Supreme Court has also, in fact, doubled down on the premise that states are the laboratories of innovation to address the ills of partisan gerrymandering,” said Kathay Feng, national redistricting director for Common Cause, which advocates overhauling the way district lines are drawn. “States are actively addressing the issue on a number of fronts.”

Thursday’s ruling heightened attention on state and federal legislation that would create nonpartisan redistricting commissions, efforts that election overhaul advocates say would curb political influence in the process.

A bill passed by the the new Democratic majority in the U.S. House this year, HR 1, would require all states to use independent commissions to draw district lines. That bill is unlikely to get a hearing in the Republican-controlled Senate, however, where Majority Leader Mitch McConnell called it “an attempt to rewrite the rules of American politics to benefit Democrats.”

H.R. 1 is the far left’s sprawling effort to seize more control of the political process. It’s an attempt to rewrite the rules of American politics to benefit the Democrats and their friends. pic.twitter.com/tztygT3YPS

— Leader McConnell (@senatemajldr) January 29, 2019

Voters in five states — Michigan, Missouri, Colorado, Utah and Ohio —passed ballot measures in 2018 that created similar panels.

Democrats said Thursday’s ruling would energize their efforts to flip state legislatures, elect Democratic governors and usher in more progressive state Supreme Court justices.

Such efforts could be especially pronounced in states like Texas, where Democrats are nine seats short of seizing control of the state House.

“The only way we’ll end partisan gerrymandering is by voting Republicans out of power in state legislatures,” Democratic Legislative Campaign Committee Executive Director Jessica Post said in a statement.