NASHVILLE (AP) — Democrats and voting rights organizations have blasted Tennessee Republicans for what they say is a brazen effort to dilute the state's Black vote by carving up booming Nashville into three likely GOP-controlled congressional districts. But their legal path for getting the new Republican-authored U.S. House map altered faces significant obstacles.

A challenge against the map would likely hinge on arguing in federal court that Republicans diluted the power of minorities based on race, according to legal experts, though an effort in state court can't be ruled out. Tennessee Republicans say their plan complies with the law and boosts Nashville's influence from one House member to three.

The new map may benefit from the hands-off approach by the U.S. Supreme Court on partisan redistricting since maps were redrawn a decade ago. Essentially, the majority said federal court won't referee the drawing of districts based on historic political leanings, notwithstanding state-level protections and whatever Congress passes in the future.

Another complicating factor — Tennessee lacks the kind of state requirements that advocates in Ohio, for one, have used in recent redistricting challenge wins. Ohio's Supreme Court declared invalid GOP-spearheaded state legislative and congressional maps in recent decisions. Those were based on 2015 and 2018 constitutional amendments that require an attempt at avoiding partisan favoritism.

In Republican-dominated Tennessee, the U.S. House delegation includes seven Republicans and two Democrats, whose districts center on Nashville and Memphis. Republican state lawmakers are looking to split Nashville into three seats, which likely makes any Democrat, including longtime Nashville U.S. Rep. Jim Cooper, a significant underdog to retain his seat against a Republican.

As it stands, Nashville's congressional district extends into two additional counties and has about a 24% Black population.

The new district where Cooper lives — jagging through slivers of southern and eastern Nashville as it branches in multiple directions into five other counties — would include about 11.8% Black residents out of those old enough to vote, according to Doug Himes, a House attorney. The other two would be 8.6% and 15.5% Black.

Democrats and voting rights groups have offered maps that keep Nashville whole, while grabbing the remaining voters needed from an adjacent county.

The Republican map could see final votes this week. Republican Gov. Bill Lee recently told reporters that right now, he sees "no reason that I wouldn't be signing it," which would cement the map for the next decade.

The push has drawn sharp condemnation from opponents who see an effort to diminish the voting impact of Nashville's Black voters. Former U.S. Attorney General Eric Holder, who served under then-President Barack Obama and is the National Democratic Redistricting Committee chairman, said Republicans in Tennessee are "effectively relegating their (Nashville Black voters') interests to the political backburner."

Odessa Kelly, a Black Nashville Democrat who has planned to run for Cooper's seat, likened the proposal to "the new Jim Crow, where racist politicians will do anything to erase us and strip power from us." Kelly, who would live in a different district, said she is considering her next steps.

And the Tennessee NAACP said the plan dilutes the strongest base of Black urban voters in Middle Tennessee by "placing them in lily-white, rural districts that are remote — as far as 103 miles — from Nashville-Davidson County."

Republicans have not directly addressed the impact their plan would have on Nashville Black voters.

Asked why he support a map that splits Black voters into three districts, Republican House Speaker Cameron Sexton told reporters "the map on the congressional satisfies the Voting Rights Act; it's fair, it's constitutional." Sexton has argued it's better for Nashville to have more representatives in Congress, without noting they would likely be all Republicans philosophically at odds with a Democratic-tilted city. Republicans have also noted that Democrats have sliced off some of Nashville in previous redistricting; however, it wasn't nearly to the degree under the current GOP plan.

The governor, who said he isn't looking closely at the map yet, added that he thinks lawmakers "are making sure that every section is represented."

The state Democratic Party has promised to sue over the map. Others could join.

However, there are fewer avenues to take redistricting complaints to court than the last time lines were drawn nationwide. In 2019, the U.S. Supreme Court ruled that partisan gerrymandering of congressional and legislative districts is none of its business.

Courts have, however, barred redistricting aimed at reducing the political representation of racial minorities for a half-century. Protections exist under the U.S. Constitution and the Voting Rights Act, which the U.S. Department of Justice has used to sue Texas over its state and congressional maps. Both have varying degrees of proof required in the courts.

"The best, and really the only real case, that they would have is that somehow there is a disadvantageous racial effect that is more than just a partisan disadvantage," said James F. Blumstein, a University Professor at Vanderbilt University's law school.

Nationally, Republicans need a net gain of five seats to flip U.S. House control.

While both parties have gerrymandered, these days Republicans have more opportunities. The GOP controls the line-drawing process in states representing 187 House seats compared with 75 for Democrats. The rest of the states use either independent commissions, have split government control or only one congressional seat.