The Pennsylvania Supreme Court is made up of mostly Democrats. They have supported an effort to redistrict the state which greatly benefits Democrats. Now Republicans have filed a document with the US Supreme Court to appeal the decision.
The times, places and manner of holding elections for Senators and Representatives, shall be prescribed in each state by the legislature thereof; but the Congress may at any time by law make or alter such regulations, except as to the places of choosing Senators.
The Congress shall assemble at least once in every year, and such meeting shall be on the first Monday in December, unless they shall by law appoint a different day.
From the Application opening paragraph:
This case arises from the Pennsylvania Supreme Court’s usurpation of the Pennsylvania General Assembly’s legislative authority to draw its congressional district lines through its preordained invalidation of the lawful districts the General Assembly enacted in 2011 (the “2011 Plan”). At all stages, the Pennsylvania Supreme Court set this case on a path whereby only it would draw Pennsylvania’s new congressional districts—a task delegated to the “Legislature”—in violation of the Elections Clause. U.S. Const. art. I, § 4. But as Justice Kennedy stated in League of United Latin Am. Citizens v. Perry, “drawing lines for congressional districts is one of the most significant acts a State can perform to ensure citizen participation in republican self-governance. * * * As the Constitution vests redistricting responsibilities foremost in the legislatures of the States and in Congress, a lawful, legislatively enacted plan should be preferable to one drawn by the courts.” 548 U.S. 399, 415-16 (2006). “Underlying this principle is the assumption that to prefer a court-drawn plan to a legislature’s replacement would be contrary to the ordinary and proper operation of the political process.” Id. at 416. The Pennsylvania Supreme Court conspicuously seized the redistricting process and prevented any meaningful ability for the legislature to enact a remedial map to ensure a court drawn map.
See more here:
1/ PA Republicans seek emergency stay from J. Alito: "unless this Court intervenes to enforce the distinction within the state between “the Legislature thereof” and the other branches, the Elections Clause will be rendered meaningless." #SCOTUS https://t.co/vasg6GnYBL pic.twitter.com/YLkcDMrqpL
— Josh Blackman (@JoshMBlackman) February 22, 2018