When it comes to taking in big bucks from big business, California’s Democrats and Republicans have a lot more in common than you might think.

More than 40 percent of the $60 million raised by California’s two major political parties for state candidates and campaigns during the 2016 election season came from corporate interests that gave to both sides, according to secretary of state finance records researched by MapLight, a nonpartisan, political-money, watchdog group.

Top double donors included:

•The California Hospital Association, which gave $3.15 million to help Democrats and $1.6 million to Republicans.

•The California Association of Realtors, which gave $1.3 million to Democrats and $850,000 to Republicans.

•AT&T, which gave $1 million to Democrats and $637,000 to Republicans.

•And Chevron Corp., which gave $885,000 to Republicans and $415,000 to Democrats.

Other major donors playing both sides of the aisle included Indian casinos, medical and dental associations, the telecommunications industry, the prison guards’ union, insurance companies, energy and utility interests and charter school advocates.

“Powerful organizations that can afford to spend millions of dollars on politics invest in both parties to curry favor with lawmakers across the state — regardless of their party affiliation,” said MapLight President Daniel Newman.

It’s worth noting that although California limits donations to candidates for office, political parties are free to take whatever they can get. Party leaders can then pump large sums into races without having to identify the original source of the funds.

Out of the 117 organizations and business interests that together gave $25 million-plus to the parties for the 2016 elections, 76 gave more to the state Democratic Party and 31 gave more to the state Republican Party. The other 10 gave the same amount to both.

In total, the Democratic Party raised $39.8 million. Republicans raised $20.9 million.

The Democrats’ edge is hardly surprising, considering they have a hammerlock on all the statewide elected offices, plus hold a two-thirds supermajority in both the state Senate and Assembly.

“Wherever you have one party in dominant control, that’s the team that is going to get the most money,” said Republican Party chair Jim Brulte. “That is just the way it is.”

As for why corporate donors would even bother with giving to the GOP: “It’s called covering your backside,” said Larry Gerston, political science professor emeritus at San Jose State University. Even though Republicans are in the minority in the Legislature, every now and again their votes might come in handy.

What counts is “who has been helpful and who has been with us,” Gerston said. “It all verifies, yet again, that interest groups are very close to lawmakers.”

John Vigna, a spokesman for the state Democratic Party, said it isn’t all about corporate money. He said new party chair Eric Bauman is working to “dramatically ramp up our small-dollar fundraising” as well.

But party activist Kimberly Ellis, who recently challenged Bauman for the party chair, said the numbers are proof that Democrats do not always practice what they preach.

“If people want to know why meaningful health care reform in California stalls, just look at our party’s donor list and you'll understand why,” Ellis said. “With the California Hospital Association’s $3.15 million investment — nearly three times the party’s next-highest contribution — we know who is really calling the shots in Sacramento.”

Ultimately, said MapLight’s Newman, “a statewide system of public funding of elections would let voters, not donors, have the greater voice in government.”

Maybe, said Gerston. But until then, “you take it from whoever gives it.”

Kopp on guard: Carve another notch in the belt of contrarian Quentin Kopp, the 89-year-old former San Francisco supervisor, ex-state senator and retired judge who is now a member of the city Ethics Commission.

A Sacramento County Superior Court judge ruled the other day in favor of Kopp and the Howard Jarvis Taxpayers Association in a suit they filed challenging a new state law allowing public money to be used for political campaigning.

SB1107, passed by the Legislature last year and signed by Gov. Jerry Brown, was intended to reduce the influence of special interests by letting cities and counties use public financing for political campaigns. Kopp and company said the law violated the 1988 voter-approved Proposition 73, which prohibits public funds from being used in campaigns.

The new bill had been championed by the good-government group Common Cause. And when Kopp joined the lawsuit in December, Common Cause tried and failed to block his reappointment to the Ethics Commission.

There is a bit of irony here. Being a charter city, San Francisco is exempted from the 1988 ban. Over the years, it has doled out millions of public dollars to finance candidate campaigns for city offices. Last year, the 12 eligible candidates received a total of $1.5 million.

And it’s the Ethics Commission that oversees the handouts.

“It’s the law, and I follow it,” Kopp said.

San Francisco Chronicle columnists Phillip Matier and Andrew Ross appear Sundays, Mondays and Wednesdays. Matier can be seen on the KPIX TV morning and evening news. He can also be heard on KCBS radio Monday through Friday at 7:50 a.m. and 5:50 p.m. Got a tip? Call (415) 777-8815, or email matierandross@sfchronicle.com. Twitter: @matierandross