At a time of broken politics and polarization, the impulse to seek out reforms to the political process is understandable. California, which will hold important primary elections on Tuesday, offers a cautionary tale about how good intentions alone are not enough.

Eight years ago, California voters approved a ballot initiative establishing a new open primary system. The new system called for primary contests in which all candidates from all parties would be listed on the same ballot. The top two finishers, regardless of party, would advance to the November election.

Then-Gov. Arnold Schwarzenegger (R) hailed the initiative’s passage as a vehicle that would change the political complexion of the state legislature and the congressional delegation. He and other proponents claimed that it would lead to the nomination and ultimately the election of candidates who were more moderate — center-left and center-right, rather than far left and far right.

“We in California have said we’ve got to come to the center, we’ve got to bring everyone together in order to solve problems,” Schwarzenegger said at the time. “And I think the rest of the nation eventually will find out this is exactly where the action is.”

The action Schwarzenegger envisioned hasn’t come to pass. Instead, the reforms have produced action of a different sort. Days ahead of Tuesday’s big round of primaries, the unintended consequences — though not necessarily unforeseen possibilities — of the open primary system are roiling the state’s politics. The system’s promises, meanwhile, remain mostly unfulfilled.

Most of the hand-wringing today is among Democrats. Their worries are a byproduct of their good fortune — the energy and enthusiasm that exists at the grass roots. Given Democratic opposition to President Trump, which is particularly strong in California, and the number of Republican-held seats that are competitive, this year’s elections have drawn bigger-than-normal fields of candidates.

In California, that’s a potential problem for Democrats. As Nate Persily, a Stanford University political scientist, put it: “This is not a system prepared for that.”

California has seven House districts held by Republicans that Hillary Clinton won in 2016. Winning as many of those as possible would be a big step toward reaching the 23 that Democrats need to take over the House.

However, in several competitive Southern California districts in Republican hands, so many Democrats are running that party leaders fear the Democratic vote will end up badly splintered. That could mean no Democrat makes it to the November ballot in those districts, which would be an unexpected self-inflicted blow to the party’s hopes of taking control of the House.

“What [Democrats] probably didn’t anticipate is that what is a big asset [nationally] this time around is turning out to be a potential liability in California,” said Chris Tausanovitch, a political scientist at UCLA.

Still, the open primary process has caused some nervousness on the other side as well. Gov. Jerry Brown (D) is in the final year of his second eight-year tenure as the state’s chief executive. Lt. Gov. Gavin Newsom (D) has a wide lead over all other candidates for Tuesday’s primary. The issue is who will join him on the November ballot.

Republicans have been worrying that another of the Democrats running could slip past their leading candidate, businessman John Cox. If that were to occur, Republicans worry that it would dampen GOP turnout in November and jeopardize other contests and ballot initiatives, including one calling for repeal of a recently enacted hike in the state gasoline tax.

Republicans fear another GOP candidate, Assemblyman Travis Allen, could take away too many votes from Cox and allow one of Newsom’s Democratic rivals to slide into second place on Tuesday. To prevent this, House Majority Leader Kevin McCarthy (R-Calif.), a Cox supporter, has weighed in with the president, according to a knowledgeable Republican official. And Trump has tweeted his support for Cox.

California, a state that long has had a reformist bent, has been on a quest for the ideal system for nominating candidates, one that would put the decision in the most hands possible. Two decades ago, through another ballot initiative, voters eliminated closed primaries (open only to members of the specified party) and replaced them with what were called blanket primaries. In those primaries, all candidates were listed on the same ballot and voters could decide whom to support. But unlike today’s open primary, the top vote-getter from each party advanced to the general election.

The Supreme Court struck down that system, declaring that it made it impossible for political parties to control their own elections. In 2011, the open primary system was installed.

Proponents claimed the open primaries would do three things: Give voters more choices, boost turnout in primary campaigns, and, most importantly, lead to the election of more moderate Democrats and more moderate Republicans. What they did not anticipate was that American politics would become even more deeply polarized over the next eight years.

Eric McGhee, a research fellow at the Public Policy Institute of California, is one of a number of experts who has studied the effects of the new system. “Among California Democrats in the legislature, they are somewhat more moderate than before the reform,” he said. “There’s no sign that we can see the Republicans have changed in the state legislature. Neither Republicans nor Democrats in the congressional delegation show much sign of change.”

Even in Sacramento, the differences are minimal. California’s legislature, according to Stanford’s Persily, is the most polarized in the nation. To the extent that there are some more moderate Democrats, that is in part the result of the business community recognizing that California remains a mostly one-party state and that getting involved on behalf of less liberal Democratic candidates is the only route to more pro-business legislators.

A new poll from Stanford University’s Bill Lane Center for the American West found 41 percent of Californians say they approve of the open primary system, compared with 22 percent who oppose it and 37 percent saying they aren’t sure what they think of it. Among those who approve, 77 percent said they support it even if it produces two candidates from the same party on the November ballot.

There are no serious efforts to alter California’s current system. Whether Tuesday’s primaries change attitudes is questionable. Bruce Cain, the director of the center, said opinion might shift at some point, but only if Democrats failed to advance a candidate to the November ballot in a major statewide race.

Until then, the reform instinct remains strong, and critics of the system, mainly those who do politics full time, would have to convince voters that fewer choices are better than more choices. “Wave any flag with ‘reform’ on it, and people in California go for it,” Cain said, adding, “It could be that chaos is just baked into our future.”

Correction: An earlier version of this article incorrectly stated that 33 percent of Californians polled by Stanford University’s Bill Lane Center for the American West say they oppose the state’s open primary system. In fact, 22 percent say they oppose it. The article has been updated.