The case is important because, if the high court finds for North Carolina, the rules governing how states regulate federal elections could change dramatically. The hearing comes at a time when tensions between Republicans and Democrats over voting procedures are growing in light of former President Donald Trump's continuing claims that the 2020 presidential election was marred by massive electoral fraud.

At issue is the once-obscure independent state legislature doctrine, under which Republicans argue that the Constitution has always directly authorized state legislatures alone to make rules for the conduct of federal elections in their respective states.

Democrats say this doctrine is a fringe conservative legal theory that could endanger voting rights, enable extreme partisan gerrymandering in the redistricting process, and cause upheaval in election administration.