Arnold Schwarzenegger — the 70-year-old international celebrity, centrist Republican, and former governor of California — has chosen an audacious third act. He’s at the forefront of a bipartisan national push to change America’s hopelessly gerrymandered government.

Schwarzenegger is perhaps the most prominent of a group of politicians who have filed briefs urging the U.S. Supreme Court to rule that extreme gerrymandering is unconstitutional. The court will hear arguments in the case, Gill vs. Whitford, next month.

Gill vs. Whitford, which concerns Wisconsin’s electoral maps for its state Legislature, is a potentially monumental case.

The U.S. Supreme Court has never weighed in on whether electoral maps — drawn every 10 years, usually by politicians of whichever party is in power — might be unconstitutional simply because they’re skewed toward one party or another.

Gerrymandering should not be a partisan issue. Drawing districts to benefit any one party or to assist a particular candidate is a cynical, bad-faith practice that makes life easier for politicians and worse for their constituents.

Once politicians from gerrymandered areas are in office, they’re often more afraid of facing a primary challenger than they are of facing a competitive general election — so they push for extreme policies.

As a country, we’ve been reaping the discouraging results — extreme polarization — for decades now.

Few are better suited to this mission than Schwarzenegger. As California’s governor, he stumped for Proposition 11, the 2008 initiative that created a nonpartisan citizens commission to draw boundaries for California’s Legislature. Two years later, voters approved an initiative that extended the commission’s powers, enabling them to draw the lines for California’s congressional districts as well.

At the time, California politicians hated the idea of Proposition 11. Democratic legislators, who were in the majority, tried to argue that it was a right-wing power grab.

The results have been anything but as advertised.

The commission has been a resounding success. Its citizen members regard their duties with the utmost seriousness. The voters have gained new trust in their state representatives.

According to a UC Berkeley Institute of Governmental Studies poll in April 2017, a whopping 57 percent of registered voters approved of the state Legislature’s job performance — the highest level since 1988. That’s a sea change from seven years ago, when the Legislature’s approval rating was just 14 percent.

As for the promised right-wing power grab, it never materialized. If anything, the balance of power in the Legislature has only tilted further toward the Democrats.

Elected officials’ legitimacy comes from being freely chosen by the voters — not the other way around.

California has learned this lesson, and it’s time for the rest of the country to embrace it.

Some brave members of Congress, as well as state elected officials, have filed briefs asking the Court to draw a hard line against gerrymandering. The list includes politicians from all over the spectrum — House Minority Speaker Nancy Pelosi, D-San Francisco, U.S. Sen. John McCain, R-Ariz., and Ohio’s Republican Gov. John Kasich, to name a few.

But it’s difficult for most politicians to surrender power, and those who no longer hold public office are the ones fighting hardest for redistricting reform. Former Attorney General Eric Holder is leading up the National Democratic Redistricting Committee, which will focus on changing redistricting procedures in several states. Schwarzenegger has a new Crowdpac, called Terminate Gerrymandering, which he’s pledged to match dollar-for-dollar.

In some ways, they’ll be facing an uphill battle — redistricting reform is a detail-based process that rarely grabs headlines. On the other hand, they’ll have a great national example in California — the state that got rid of gerrymandering and improved political trust.

This commentary is from The Chronicle’s editorial board. We invite you to express your views in a letter to the editor. Please submit your letter via our online form: SFChronicle.com/letters.

In 2008, California voters passed Proposition 11, creating an independent citizens’ commission to draw state legislative district boundaries. The commission has 14 members: five Democrats, five Republicans, and four who belong to neither party.

Ballotpedia conducted a study of competitive districts in 2014. (New district maps were completed after the 2010 census.) It found that there were four competitive elections for California’s State Assembly in 2012, up from two in 2010.

In 37 out of 50 states, state legislatures are responsible for state redistricting.