The Supreme Court’s conservative bloc may be preparing an attack on state sovereignty in order to maintain a Republican gerrymander through the 2018 midterms.

Last week, the Pennsylvania Supreme Court invalidated the state’s current congressional map, ruling that it favored the GOP in violation of the state constitution and ordering a new, nonpartisan map. Republican legislative leaders asked Justice Samuel Alito, who reviews emergency appeals out of Pennsylvania, to block the decision. Because the Pennsylvania Supreme Court decision involved only state law, Alito should’ve denied the request outright. Instead, he has ordered voting rights advocates to respond, raising the real possibility that a majority of the justices will vote to halt the ruling. If they do, the intervention will mark an extraordinary expansion of the court’s power to prevent states from protecting their residents’ voting rights.

To understand why the U.S. Supreme Court’s intrusion would be so radical here, it’s important to remember a key feature of the Pennsylvania Supreme Court’s holding. The court did not rule that the state’s gerrymander infringes upon any provision of the U.S. Constitution. Instead, the court held that partisan redistricting runs afoul of the Pennsylvania Constitution, which guarantees “free and equal” elections as well as an unusually robust right to free expression and association. These protections go beyond the rights of free speech and suffrage contained in the U.S. Constitution.

By rooting its decision in the state constitution, the Pennsylvania Supreme Court should have insulated its holding from review by the U.S. Supreme Court. Basic principles of federalism, or the balance between states and the national government, bar federal courts from overruling state supreme courts on an interpretation of state law. Thus, the U.S. Supreme Court can only reverse state supreme court decisions that misconstrue federal law or the federal Constitution.

The Pennsylvania Supreme Court decision did no such thing. But Republican leaders in the state legislature have concocted a bizarre theory in order to claim that it did. To justify the intervention of the U.S. Supreme Court, they allege that the state supreme court’s decision violates the Elections Clause of the U.S. Constitution. That provision states that “the times, places and manner” of federal elections “shall be prescribed in each state by the legislature thereof,” unless overridden by Congress. Republicans assert that the Pennsylvania Supreme Court flouted this clause by seizing a legislative power—the drawing of congressional districts—for itself.

This framing has several major flaws. First, SCOTUS rejected a very similar theory in 2015’s Arizona State Legislature v. Arizona Independent Redistricting Commission, or AIRC. In that case, Arizona voters passed a constitutional amendment that stripped redistricting power from the state legislature and assigned it to a nonpartisan commission instead. Arizona legislators sued, alleging a violation of the Elections Clause.

The court rejected their claim. It held that the clause did not grant exclusive redistricting authority to the state legislature. The majority explained that “nothing in that clause instructs, nor has this court ever held, that a state legislature may prescribe regulations on the time, place, and manner of holding federal elections in defiance of provisions of the state’s constitution.” Put differently, a state legislature may be compelled to comply with the state constitution’s limits on redistricting—even if that constitution abolishes the legislature’s redistricting power altogether.

Of course, the Pennsylvania Supreme Court did not actually strip the legislature of its redistricting authority. It merely directed the legislature and the governor to devise fairer maps, noting that it would commission its own if they failed. SCOTUS affirmed the constitutionality of a much harsher scheme in AIRC. If a state constitution may prohibit the legislature from redistricting altogether, then a state supreme court can surely place modest limitations on the legislature’s ability to engage in partisan gerrymandering.

Even if AIRC weren’t on the books, Republicans’ theory would pose a grave threat to federalism by undermining the balance of power among state governments. To see how, just look at their own petition to SCOTUS. Although the appeal is ostensibly based in the federal Elections Clause, a majority of its arguments (and pages) rebut the Pennsylvania Supreme Court’s interpretation of the Pennsylvania constitution. (The court, it gripes, engaged in “judicial activism” by “magically” weaving new rules “from whole cloth.”) GOP legislators’ real complaint is that, in their view, the court misinterpreted the state constitution. But SCOTUS has no power to reverse a state supreme court’s interpretation of state law. Republicans are dressing up a state law conflict in the guise of a federal dispute.

Even though the GOP’s arguments appear to be pretextual, it’s worth considering their revolutionary implications. Pennsylvania Republicans claim that the U.S. Constitution bars state supreme courts from regulating partisan gerrymandering—meaning state legislatures have untrammeled authority to engage in political redistricting.

If true, this theory would neuter state constitutions across the country. Some state constitutions, like Florida’s, explicitly proscribe the legislature from drawing partisan gerrymanders. Others, like Virginia’s, require compact districts that preclude overly political redistricting. Every single state constitution vigorously protects the right to vote, language that may be interpreted to bar gerrymandering. The task of enforcing these provisions falls upon state supreme courts. But under the theory advanced by Pennsylvania Republicans, the courts cannot be used to curb gerrymanders because the legislature retains sole authority to draw congressional maps. No court has ever suggested that’s the case.

And yet, here we are: Alito indicated that he takes this appeal seriously by ordering a response, suggesting that five justices may vote to freeze the Pennsylvania Supreme Court’s ruling. What could possibly justify their intervention?

The disturbing answer comes from the Bush v. Gore playbook. Recall that in Bush v. Gore, SCOTUS overturned a Florida Supreme Court decision ordering a recount of ballots. The majority relied upon an equal protection rationale. But three justices—Chief Justice William Rehnquist, as well as Justices Antonin Scalia and Clarence Thomas—also cited a constitutional provision similar to the Elections Clause that instructs the state legislature to dictate the rules of presidential elections. Rehnquist, Scalia, and Thomas insisted that under this clause, the Florida Supreme Court lacked authority to demand a recount in contravention of the legislature’s wishes. This trio later reiterated its belief that the federal Constitution restricts state supreme courts’ power to regulate redistricting.

As election law expert Rick Hasen noted, Pennsylvania Republicans’ argument plainly draws from Bush v. Gore to question the Pennsylvania Supreme Court’s ability to supervise congressional elections. It’s a frightening theory that could, taken to its logical endpoint, forbid every state’s highest court from safeguarding the right to cast an effective ballot. Alito should have dismissed it immediately. His willingness to entertain this appeal instead bodes poorly for both democracy and federalism. The U.S. Supreme Court has no business forcing Pennsylvania voters to languish under a gerrymander that can’t pass muster under Pennsylvania law.