A long list of prominent Republicans is urging the Supreme Court to find that extreme partisan gerrymandering is unconstitutional, saying the practice of drawing electoral lines to benefit one party or another is detrimental to democracy.

It puts those Republicans on opposing sides from groups such as the Republican National Committee and the party's congressional campaign committee, which are supporting Wisconsin's GOP-led legislature in a major high court case to be heard next month.

A lower court found lawmakers drew maps that so favored Republican candidates that they violated the constitutional right of equal protection.

Now, Republicans such as former California governor Arnold Schwarzenegger and the party's former presidential nominee Robert Dole have signed onto friend-of-the-court briefs that say the Supreme Court should find — for the first time — that a redistricting plan is so politically biased it must be thrown out.

"Partisan gerrymanders frustrate majority rule by entrenching political parties in ways they do not earn on the merits," says the brief signed by Schwarzenegger and other former elected Republican officials. "They turn republican government upside down, with politicians choosing their voters instead of voters electing their politicians."

In a conference call with reporters, Schwarzenegger said that in the case at the Supreme Court, it is Republicans who have drawn maps to their benefit. "But when Democrats have the power, they gerrymander, like in Illinois and Maryland."

Indeed, challengers of the Democrat-drawn congressional maps in Maryland filed an unusual motion with the Supreme Court last week, asking that their case be heard as well as the Wisconsin case, Gill v. Whitford.

A three-judge panel last month split 2 to 1 to allow Maryland to use its voting boundaries for the 2018 election and put the lawsuit on hold until after the Supreme Court rules in the Wisconsin case.

The challenge in Maryland centers on redrawing a congressional district anchored in Western Maryland in such a way that transferred Republican voters out and Democratic voters in, resulting in a victory by a Democrat over the incumbent Republican congressman.

The challengers' petition to the Supreme Court says that considering their case along with the one from Wisconsin would provide a "broader spectrum of legal arguments and evidence with which to address the problem of partisan gerrymandering."

Such last-minute petitions are rarely granted by the court.

The outpouring of amicus briefs in the Wisconsin case — on both sides — underscores its importance. A host of Republican-led states have urged the Supreme Court not to get involved with what they say are essentially political decisions made by elected representatives.

"There is nothing invidious, or irrational, under the Equal Protection Clause, about legislatures having partisan purposes when reapportioning legislative seats," said a brief filed by Texas and other states.