Veteran political consultant Rob Stutzman has helped plenty of Republican candidates, from local officials to governors. Now he has teamed up with two equally seasoned GOP strategists to try to stop a Republican they fear will destroy the party for years to come.

That candidate is Donald Trump.

It won’t be easy, considering Trump’s significant lead in statewide polls. But Stutzman and fellow consultants Ray McNally and Richard Temple have a plan that is unorthodox even by this year’s wacky standards.

They are not necessarily promoting Texas Sen. Ted Cruz, Ohio Gov. John Kasich or any other presidential candidate. What they are determined to do is keep Trump from securing the 1,237 delegates required for party nomination at the Cleveland convention this summer. Their strategy took shape in recent months as “you could see the arc of this race would very likely come to California,” Stutzman said in a phone interview last week.

And it has. So it’s game on for the stop-Trump movement.

“There’s no question there are voters who want to know what’s the most efficient way to vote for an open convention,” Stutzman said.

As Americans have seen in this primary season — and Trump has complained every time his campaign has been outwitted — delegate-allocation rules vary wildly from state to state and from party to party.

In California, the statewide winner receives only 10 of the 172 available delegates. The bulk of the delegates are awarded to the top vote-getter in each of the 53 congressional districts. A win in a district yields three delegates.

“The reality is, we’re talking about 53 distinct races,” Stutzman said. “That provides some unique opportunities.”

What the Stutzman-McNally-Temple team plans to do is determine — through polling, demographics and other data — which candidate, Cruz or Kasich, has the best chance to defeat Trump in each district. They are raising money (http://victorycalifornia.com) for mailers and social-media campaigns to ensure that anti-Trump Republicans know which alternative has the best chance in their district.

Because neither Cruz nor Kasich has a chance of reaching 1,237 before Cleveland, the only hope for each is to deny Trump a first-ballot victory and hope for a free-for-all on subsequent ballots.

This is where the strategy gets a bit crazy. A relative centrist Republican who supports Kasich but despises Cruz as too rigidly right might be advised to swallow hard and vote for Cruz “to give John Kasich an opportunity on a third or fourth ballot,” Stutzman explained.

Conversely, die-hard Cruz supporters might be encouraged to vote for Kasich in certain districts.

Yet another twist: All Republican votes are not equal in this primary. Congressional District Four, a wide swath of the Sierra from north of Lake Tahoe to south of Yosemite, has 175,000 registered Republicans. House Democratic Leader Nancy Pelosi’s 12th District has about 30,500 Republicans.

Yet each of those districts will send three delegates to Cleveland.

“If you’re a Republican in Nancy Pelosi’s district, this is the reward you finally get,” Stutzman said. “People are going to pay a lot of attention to you. The irony of that is pretty rich.”

Stutzman initially supported Jeb Bush, then, when he dropped out, turned to Sen. Marco Rubio. When Rubio left the stage, Stutzman’s primary goal became stopping Trump. He acknowledged that Cruz would be a long shot against anticipated Democratic nominee Hillary Clinton, but at least the senator would preserve much of the Republican base, and avoid huge losses in congressional and legislative races. Polls show that 20 percent of Republicans, said Stutzman, “will not vote for someone who is a misogynist, a liar, a bigot, a vulgarian and appears to not have a grasp of fundamental issues that are required to occupy the Oval Office.”

The anti-Trump GOP consultants’ playbook essentially comes down to this: The enemy of my enemy is my friend, no matter what.

It’s a long-shot quest. One sure prediction: If it succeeds, Trump will cry foul about “stolen delegates” and a “rigged system.” Yet all sides know going into the California GOP primary is that it involves 53 races and great attention to detail.

John Diaz is The San Francisco Chronicle’s editorial page editor. Email: jdiaz@sfchronicle.com Twitter: @JohnDiazChron

The June 7 California primary: A primer

Registration deadline: May 23

You can register online at www.registertovote.ca.gov.

Vote by mail: You can get a vote-by-mail application at the Secretary of State’s website: www.sos.ca.gov.

Ballots will be mailed to voters the week of May 9; they must be received by May 31.

Republican presidential primary

Under party rules, only registered Republicans can vote in this closed primary.

Delegate allocation (172 total): 159 selected on a winner-take-all basis in each of the state’s 53 congressional districts (three per district); 10 go to the statewide winner; the remaining three are reserved for the state party chair and two national committee representatives.

Democratic presidential primary

Under party rules, voters who selected “no party preference” when they registered to vote can request a Democratic ballot and vote in its presidential primary. The Libertarian and American Independent parties also offer that option to unaffiliated voters.

Delegate allocation (475 at stake): Delegates will be awarded proportionate to each candidate’s vote total, with a 15 percent minimum vote to qualify. California also has 73 superdelegates who are not bound by the primary results.

U.S. Senate primary

Under the state’s top-two system (established by voters in 2010), candidates of all parties appear on all ballots. The top two finishers, regardless of party, will compete in the November general election.

Note: The first major debate of the race to succeed Sen. Barbara Boxer is scheduled for 6 p.m. Monday at the University of the Pacific in Stockton. Democrats Kamala Harris and Loretta Sanchez and Republicans Ron Unz, Tom Del Beccaro and Duf Sundheim have confirmed. The Chronicle-KCRA debate will be televised statewide (NBC3 in the Bay Area) with The Chronicle’s John Diaz and KCRA’s Edie Lambert serving as moderators. The Chronicle, KCRA and UOP all plan to live-stream the debate on their websites.