The U.S. Supreme Court heard lawyers' arguments last week in a case that could reshape American politics. The issue is whether Republican legislators in Wisconsin gave their party an unfair advantage in 2011 when they drew political district maps – something all states do every 10 years to reflect population totals in the latest federal Census. The nine justices in Washington, D.C., will decide by next spring whether maps that entrench one party's control of a legislature or congressional delegation can violate the constitutional rights of the other party's voters. The impact will spread nationwide. "Democracy on the line" says a headline atop coverage in U.S. News & World Report magazine.

After the 2010 Census, Republicans controlled more state governments than Democrats did and aggressively redrew district maps to lock in election advantages for a decade. That process is called "gerrymandering," a word created in 1812 by a Boston newspaper after Massachusetts State Senate districts were redrawn under Gov. Elbridge Gerry to favor his side. More than two centuries later, a New York Times editorial about "this age-old problem" says: "All map drawing is political, but at its most extreme, it strikes at the heart of representative democracy. By letting politicians pick their voters rather than the other way around, this practice, known as partisan gerrymandering, corrodes the relationship between lawmakers and their constituents. It also discourages bipartisanship and undermines the public's trust in government." At last week's court session, an attorney lawyer arguing against Wisconsin's process told the justices: "You are the only institution in the United States that can solve this problem just as democracy is about to get worse." The lawyer, Paul Smith of a Washington public interest group called the Campaign Legal Center, predicts a "serious incursions on democracy if this court doesn't do something. This is really the last opportunity."

Seven in 10 Americans oppose partisan gerrymandering, opinion surveys show. In Wisconsin, election borders crafted by Republicans six years ago for the state Assembly worked so well that the party won 60 of the 99 seats in 2012 – even though Democrats got 51.4 percent of the statewide votes. A federal district court later struck down the current maps as unfair and illegal. A federal appeals court agreed in a 2-1 vote last November – setting the stage for Supreme Court review.

The justices never have thrown out a political map as too partisan, though they and lower courts have struck down districts as racially biased. In the last redistricting challenge to get this far, the top court split in 2004 over how much partisanship in map drawing is too much or how to measure it. This time, Justice Anthony Kennedy – a pivotal "swing vote" between liberal and conservative colleagues – seems to suggest that the court could set a standard for illegal gerrymandering by gauging whether a map is drawn with the "overriding concern" to "have a maximum number of votes for party X or party Y."

Conservative justice says: "Gerrymandering is distasteful, but if we are going to impose a standard on the courts, it has to be something that's manageable." – Samuel Alito Jr., U.S. Supreme Court

Columnist writes: "This could be the most important case with the most far-reaching ramifications of any the court decides this term." – Linda Killian, U.S. News & World Report magazine

Editorial says: "This is the opposite of how democracy is supposed to work. . . . The court must step in." – The New York Times