The Supreme Court will consider whether gerrymandered election maps in Wisconsin violate the Constitution. The Post's Robert Barnes explains. (Gillian Brockell/The Washington Post)

On Tuesday, the Supreme Court will take up what may be the most important case of its new term, in which justices will answer the question: Just how far can the Republican Party go in its assault on democracy?

I’m sure my Republican friends will find that an unfair characterization. But that really is what is at issue here, because gerrymandering is only one facet of a more comprehensive effort that includes vote-suppression laws targeted at minority groups and students. The broader effort is intended to rig elections so that Republicans always have the advantage, enabling them to hold on to power even when a majority of voters would prefer Democrats.

The case the Supreme court will be hearing, Gill v. Whitford, involves a challenge to the redistricting of state legislative lines undertaken by Wisconsin Republicans after they took control of the legislature in 2010. It’s appropriate that it comes from Wisconsin, because that state may be the best microcosm of our broader political situation: Though Wisconsin is closely divided between Democrats and Republicans, the state’s Republicans have been utterly ruthless in attempting to make their control of the levers of power permanent, the will of the voters be damned.

The Wisconsin redistricting was stunningly effective. In 2012, for instance, Democratic candidates won 53 percent of the statewide votes for the assembly, yet Republicans won 60 of the 99 seats. The voter ID law Republicans passed helped keep thousands of legitimate voters (disproportionately African-Americans) from the polls.

But the obvious unfairness of the state’s district lines does not guarantee any result in the Supreme Court, for two reasons. First, up until now the court has not been willing to say that partisan redistricting, even if it produces grotesquely undemocratic results, is unconstitutional. Second, the court has at least four justices who will always rule that whatever benefits the Republican Party is A-okay. So as so often happens, it comes down to Anthony M. Kennedy.

In previous cases when claims on partisan redistricting were made, the Supreme Court ruled that this is a political question for politicians to sort out, not one for the courts. But the last time it came up, Kennedy wrote, “I would not foreclose all possibility of judicial relief if some limited and precise rationale were found to correct an established violation of the Constitution in some redistricting cases.”

In other words, he found it hard to come up with a standard that could be applied for lower courts to decide whether a particular case of partisan redistricting had gone too far in undermining the equal protection rights of the citizens whose votes were being made worthless.

In Gill v. Whitford, the lower court came up with a three-part test, asking these questions: Did the redistricting have partisan intent? Did it have partisan effects? And do the lines lack some legitimate justification, such as the geography of the state? They answered yes to all three questions and struck down the lines.

It should be said that this three-part test is only one of many one might use to determine whether a state’s redistricting plan violates the equal protection clause. But you can make an argument for why the Supreme Court should go even further, as unlikely as it might be.

Partisan gerrymandering has long been a feature of our democracy — decried by all as unfair and undemocratic, but tolerated because it seemed inevitable and because every side hopes that it can construct its own gerrymanders once it gains power. While today’s Democrats have undertaken some gerrymandering (most notably in Maryland), Republicans have been more shameless about it, particularly in states such as Pennsylvania, Michigan and Florida. By some estimates, that has given the GOP as many as 22 seats in the House of Representatives that they otherwise wouldn’t have won, and that’s before we get to state races. It’s been made possible by the use of sophisticated software that can quickly and easily carve up a state so that once a party has power, it can in effect pick its voters to guarantee its hold on that power even after it loses the support of the people.

The combination of those contemporary tools and the willingness to use them means that we have a situation in which a party can win a majority and then change the rules to say, in effect, “Henceforth, we win if we have more than 45 percent of the vote. The other side loses if it has less than 55 percent.”

It would be a significant leap for the Supreme Court to rule that partisan gerrymandering is by definition incompatible with equal protection, even as evidence mounts that that is indeed the case. If they did, it would mean that every state would have to use the nonpartisan (or bipartisan) commissions that now draw district lines in a small number of states for Congress and/or state legislatures. These commissions come in different types with varying levels of influence exercised by politicians, but if done right they can guarantee a fair process and fair results. And the same software that is used to create gerrymandered districts can be used to create districts that are as equitable as possible. We’ve reached the point where if a state isn’t using a nonpartisan commission, the system is either already rigged or is just waiting to be rigged.

Sometimes it can be useful to step back and ask, “If we were designing our democracy from scratch, is this how we’d do things?” It can be tempting to assume that the way we’ve always done it is just the natural order. But if you can remove yourself from the assumption that there’s something sacrosanct about the status quo, you can begin to see more clearly. So imagine there were a country transitioning from dictatorship to a multiparty democracy with a parliament, and its leaders asked you how they should go about designing districts. Would you say to them, “What you want is to have the party holding power at any particular moment draw the district lines so they can maximize their advantage and shut the other party out”?

Of course you wouldn’t. That wouldn’t be fair; it wouldn’t represent the will of the people; and it wouldn’t uphold our constitutional principle of equality. But if the Supreme Court punts on the partisan redistricting question the way it has in the past, it will be a clear signal for the parties — especially the Republican Party, which has shown how enthusiastic it is about gerrymandering — to go all out and carve up states to make sure they always win, no matter what the voters want.