Three veteran California Republican operatives, Rob Stutzman, Richard Temple and Ray McNally are working to keep Donald Trump from winning any of California’s 172 Republican National Convention delegates:

“I think it’s possible Trump gets shut out in California,” Stutzman told NBC News.

Sen. Ted Cruz is doing his part. He’ll make two campaign stops in California on Monday — a rally in Irvine and another in San Diego. Stutzman said that California’s system makes it more possible to defeat Trump by focusing very specific, targeted messages to Republicans in each district. Only 13 of California’s 172 delegates are awarded to the winner of the state, the rest are doled out based on the winner of each Congressional district.

This is the winning formula that worked so well in Wisconsin focusing on delegate-wins instead of state wide wins. Trump has failed to master the complicated minutia of delegate allocation — a major weakness of his candidacy.

Stutzman plans to ramp up the California stop Trump effort in the next ten before early voting starts there on May 9. California’s late presidential primary hasn’t really mattered since 1972 when Sen. George McGovern won California and the Democrats nomination.