California’s 2008 effort to take the politics out of redistricting is the hit of the land.

On election day, voters in four states — Colorado, Michigan, Missouri and Utah — decided they wanted to be more like the Golden State, passing ballot measures to cut legislators out of the very political business of drawing the lines for their districts after the 2020 census.

In May, Ohio voters overwhelmingly backed a measure requiring bipartisan support when making the lines for House seats.

“For years, redistricting fell beneath the radar, but now it’s one of the hottest and sexiest topics in politics,” said David Daley, a senior fellow with FairVote, a nonpartisan election reform group. “Voters hate the idea of politicians choosing their voters.”

Nonpartisan redistricting hasn’t always been a popular cause, especially with politicians, who were happy drawing their own district lines with no actual voters involved.

When Proposition 11, the 2008 initiative that established California’s citizens redistricting commission, made it to the ballot, Democrats were outraged, arguing that it wasn’t right to have unelected voters make such important political decisions.

More to the point, Democrats suggested quietly, having a nonpartisan commission drawing the lines could make it tougher to squeeze out Republicans.

In a June 2008 email, then-state Senate President Pro Tem Don Perata, D-Oakland, described Prop. 11 to Democratic leaders as the “last best chance to prevent us from protecting and expanding our majorities in the Legislature in the decade to come.”

Perata had plenty of company in those concerns. Prop. 11, for example, called for the new commission to redraw only state Senate and Assembly districts. Congressional seats were left out after then-House Speaker Nancy Pelosi of San Francisco threatened to raise millions of dollars to defeat the initiative if her members were included.

Two years later, when Proposition 20 gave the commission authority over California’s congressional seats, Pelosi, joined by almost every other Democrat in the delegation, put $10,000 into the unsuccessful effort to block the measure.

In 2010, as a Democratic state senator from Los Angeles, Alex Padilla spent $39,000 in campaign funds on Proposition 27, an unsuccessful effort to give redistricting back to the Legislature.

But now, as secretary of state, Padilla touts the commission as an example of the state’s commitment to election reform, along with innovations such as a growing reliance on mail ballots, a willingness to take more time to accept and count ballots, and voting machines with a guaranteed paper trail.

“We’re getting calls from other states all the time about what we’re doing in California,” Padilla said.

California’s move to nonpartisan redistricting was a major victory for election reform, said Michael Li, a senior counsel and redistricting expert at the Brennan Center for Justice at New York University.

“The commission drew the maps in 2011, and it wasn’t the end of the world,” he said. “If a really large and really demographically complicated state like California could succeed, why not other states?”

The idea of nonpartisan commissions also got a boost when voters in states across the nation saw the alternative.

The districts drawn by politicians in 2011 “were the worst in history,” Li said. In states like Michigan, Maryland and North Carolina, the party in charge drew lines that “not only gave them an advantage, but ensured that there was almost nothing (the opposing party) could do to move through it.”

An example of the power of partisanship showed up in Pennsylvania, where Republicans controlled the 2011 redistricting. Reapportionment gave Republicans overwhelming control of both legislative houses in the 2016 elections and a 13-5 edge in the congressional delegation, even as Donald Trump barely won the state’s presidential vote.

But in January, the Pennsylvania Supreme Court overturned the congressional map, saying it “clearly, plainly, and palpably” violated the state’s Constitution and that the GOP plan was “aimed at achieving unfair partisan gain.”

The court appointed Nathaniel Persily, a Stanford University election law professor, to redraw the lines for the midterm elections. When the votes were counted, the Pennsylvania delegation was evenly split, nine to nine.

“That 50-50 split represented the preference of the voters in the state,” said Daley of FairVote. “But there wasn’t a change in the legislature lines, where Democrats still won more votes and Republicans won more seats.”

The seeming unfairness has both Democrats and Republicans looking for changes, said Li of the Brennan center. Besides the states that voted to make changes this year, GOP-leaning states, including Arkansas and Oklahoma, have citizens groups looking to qualify redistricting initiatives, and Virginia activists are working to push a constitutional amendment through the Legislature.

“There’s definitely grassroots momentum, and these efforts are popping up in strange places,” Li said.

When conservative states like Utah are willing to make a switch an independent redistricting commission, there’s something happening nationwide.

“It’s causing people to say, ‘Maybe we should do it like California,’” Li said.

John Wildermuth is a San Francisco Chronicle staff writer. Email: jwildermuth@sfchronicle.com Twitter: @jfwildermuth