The Supreme Court’s decision to allow a redistricting commission set up by Arizona voters holds the potential of reducing the rampant gerrymandering that has virtually guaranteed a Republican-controlled U.S. House until at least 2022.

And that would be a good thing, since partisan redistricting in a half-dozen states has skewed the makeup of the House of Representatives, which James Madison said was supposed to display “fidelity and sympathy with the great mass of the people.”

But it probably won’t happen.

The reason: It’s almost impossible to take politics out of the process by which legislatures re-draw legislative and congressional district lines after every census to reflect population changes. Every unequal redistricting has essentially resulted from an election.

Most of today’s anomalies stem from Republican 2010 successes in electing the legislators who redrew lines in key states after that year’s census. They produced these GOP House majorities in states that voted Democratic in most recent presidential elections: Florida, 17-10; Michigan, 9-5; North Carolina, 10-3; Ohio, 12-4; Pennsylvania, 13-5; Virginia, 8-3; Wisconsin, 5-3.

An even division of seats in those states would have reduced the current GOP margin by two-thirds and given the Democrats the House in 2012, when they received a majority of congressional votes.

But Republicans, who spent all but four years in the House minority from 1931 to 1995, are unlikely to cede power without a fight.

“For 40 years, the Democratic Party had the pencil in their hands, and for the last 20 years, we had the pencil,” House Speaker John Boehner told the Cincinnati Enquirer last December in opposing any changes in the legislature’s redistricting process in his home state of Ohio. “When you’ve got the pencil in your hand, you’re going to use it to the best of your advantage.”

Of course, redistricting isn’t done by pencil anymore, if it ever was, but by sophisticated computers that enable the majority to maximize its advantage. That makes it easier to produce the majority party’s desired result.

But gerrymandering itself is hardly new; the term stems from the 1812 handiwork of Gov. Elbridge Gerry in redrawing Massachusetts’ state Senate districts to benefit his Democratic-Republican Party, the forerunner of today’s Democrats.

As Boehner correctly notes, Democrats did their best to maintain their House majorities for decades, especially in the South and in California, where the late Rep. Phil Burton crafted a Democratic congressional majority before the state turned reliably Democratic.

In Texas, Democrats did an especially masterful job in 1991 by creating three new minority-controlled Democratic districts while temporarily protecting three white Democrats at a time the state was becoming increasingly Republicans.

In 2011, the GOP-controlled legislature gave Republicans all four new congressional districts. But, unlike the Democrats, they didn’t protect minorities at a time that 65 percent of the state’s increased population was Hispanic, so a federal court threw out the plan as violating the Voting Rights Act.

Another federal court produced a revised map, giving each party two of the new districts, and the legislature eventually acquiesced.

Some post-2010 cases are still pending, In Virginia, a federal court threw out the legislature’s redistricting plan, throwing the issue back to lawmakers. Democrats might ultimately gain an additional seat or two.

But that won’t have much effect, nor will most commissions created at the behest of good government groups, simply because they are in states with delegations too small to produce major changes.

The Arizona ruling will only have a real impact if voters in the largest states act to take redistricting out of the hands of their legislatures. There seems little likelihood of that happening anytime soon.

And though some Democrats think they could regain the House with a landslide presidential victory in 2016, few expect that result. Instead, they’ll have to do the nitty-gritty work in the 2018 and 2020 gubernatorial and legislative elections, which will determine who controls redistricting after the 2020 census.

But even that will be hard, given the fact that most of those legislatures will be elected in districts determined by those 2010 GOP successes.

— Carl P. Leubsdorf is the former Washington bureau chief of the Dallas Morning News.