Among the experts who think the means now exist for courts to referee gerrymandering fairly is Keith Gaddie, whose work enabled Wisconsin’s Republican mapmakers. In a brief submitted to the Supreme Court in August, Gaddie and Grofman argue that social scientists can identify exactly how much the differential treatment of voters is ‘‘man-­made’’ — a result of deliberate efforts by the party in power to penalize the opposition. I called Gaddie to ask how his stance squares with his earlier role. ‘‘I didn’t draw any maps in Wisconsin,’’ he said. ‘‘I helped them construct measures and tools. They made decisions and drew lines.’’ When I asked if he would do the same thing again, Gaddie said, ‘‘I don’t do this work anymore,’’ and hung up.

In their brief to the Supreme Court, Republicans in the Wisconsin Legislature called the lower court’s decision to strike down the 2011 maps ‘‘not only wrong, but dangerously so.’’ Accepting the efficiency gap as a metric of partisan bias, the brief argues, unfairly penalizes Republicans for the geographic advantage that Democratic voters have provided by packing themselves into cities like Milwaukee and Madison. Allowing cases like Gill to proceed will serve only ‘‘to increase the federal judiciary’s already outsized role in the redistricting process.’’

One expert on the Republicans’ side, Nicholas Goedert, a political scientist at Virginia Tech, is critical of the efficiency gap and the other metrics of partisan bias, especially based on the results of only one election. Some redistricting maps from this decade scored high for bias one year and then looked much better after a second election. ‘‘Look, I’m a progressive Democrat,’’ Goedert says. ‘‘But I’m not going to advocate for courts playing an inappropriate role and using an inappropriate test.’’ Goedert argues that rather than turning to the courts, opponents of gerrymandering should push for commissions. Bipartisan or nonpartisan appointees now draw statehouse lines in 13 states and congressional lines in six, including Arizona, California and New Jersey. States with commissions tend to have more competitive races with less partisan bias, scholars have found.

The Supreme Court’s conservative wing will probably argue that judges should stay out of redistricting, just as it did in Vieth. Kennedy could join this group and simply shut the door on partisan gerrymandering challenges. Or he could join the four liberals, who are likely to see Wisconsin’s redistricting as unconstitutional, and find that, at long last, the social scientists have come up with the ‘‘workable standard’’ he previously sought. The court could also tell Wisconsin that it went too far without settling on a particular metric to be used in all future cases, leaving it to lower courts to decide.

Kennedy may also decide that courts should recognize party identity, not race, as the real reason for gerrymandering in many instances. Last year, a federal court struck down two congressional districts, drawn by the Republican-­controlled Legislature in North Carolina, for excessively packing black voters. The Supreme Court agreed with the lower court in May. Kennedy dissented in part, joining the conservatives to argue that North Carolina packed the voters not because they were black but because they were Democrats. ‘‘Maybe a persuasive argument to Kennedy now is, ‘O.K., we’ve been fighting over gerrymanders through the poisonous lens of race,’ ’’ Persily suggests. ‘‘ ‘We’d be better off calling them what they really are — partisan gerrymanders.’ ’’ Division by party could be less fraught, as a focus for judges and Legislatures, than polarization by race.

The stance that the Supreme Court takes toward Wisconsin’s State Assembly map will determine how courts look at the maps for congressional delegations in every state, in 2018 and beyond. The next round of redistricting, after the 2020 census, promises to be even more brutally efficient in maximizing partisan advantage than the last one. At the moment, experts estimate that to take back the House by a bare minimum of seats, Democrats would need to win the national popular vote by at least six points.

To Dale Schultz, that sounds like handicapping democracy. Schultz is now co-­chairman of Wisconsin’s Fair Elections Project, and he has been traveling his state, stumping for a nonpartisan redistricting commission. ‘‘Maybe if the Supreme Court sees the wisdom of our argument in Gill, that would start a chain reaction, and once and for all, we would take redistricting away from legislators,’’ he says. ‘‘Right now, they’re picking the voters, instead of the other way around.’’