For months, California’s Republican leaders had, with fingers crossed, hoped that the state’s top GOP officeholder, San Diego Mayor Kevin Faulconer, would change his mind.

They wanted him to run for governor in 2018, contending that with Democrats drifting leftward in reaction to President Donald Trump, a centrist Republican would have a chance to win.

And even if he couldn’t win in a blue state, it was thought, if he could make it to the November ballot he would spur Republican voter turnout and help some embattled GOP congressional members keep their seats.

But Faulconer, who had consistently denied interest in running, wouldn’t change his mind and last week buried any hopes that he would.

“I’m honored that so many across our state are strongly encouraging me to run for governor,” he said in a statement on Friday. “However, my first commitment is to San Diego.”

Faulconer’s opt-out makes even more likely the scenario of a Democrat vs. Democrat runoff next year, thanks to the state’s top-two primary system.

With Faulconer out, as many as three weak Republicans will be running, dividing the already scant GOP voter pool and making it likely that Democrats will finish one-two in June and face each other in November.

San Diego County businessman John Cox and Travis Allen, a very conservative assemblyman from Huntington Beach, have declared their candidacies, and Faulconer’s refusal means that David Hadley, a moderate former assemblyman from Manhattan Beach, will jump in as well.

We’ve seen this rodeo before, just a year ago, when three little-known Republicans ran for the U.S. Senate, thus allowing two Democrats, Kamala Harris and Loretta Sanchez, to top the primary field and face off in a general election that Harris won handily.

Without a Republican on the 2016 Senate ballot and with a very unpopular Trump as the GOP presidential candidate, Democrats gained legislative seats.

The stakes will be higher for Republicans next year. Democrat Hillary Clinton defeated Trump in seven of the state’s 14 Republican-held congressional districts, and several of their incumbents have been targeted as Democrats make a nationwide push to claw back control of the House.

Democratic leaders have said that their hopes of netting the 24 seats required for control are rooted in an assumption that they can win several in California by wrapping Trump and GOP votes to repeal Obamacare around the necks of vulnerable Republicans.

Not having a Republican running in November for governor, the most important office to be filled next year, will depress GOP voter turnout, and that could be critical in close congressional elections.

Faulconer’s decision not to run also benefits one of the would-be Democratic governors  — although which one is still uncertain — by making a second-place finish in the June primary more possible.

Finally and indirectly, it also benefits Republican voters, although they may not know it. If, indeed, two Democrats are vying for the governorship in November 2018, GOP voters could be decisive in which one claims the office and, perhaps, a rung on the presidential ladder.

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Dan Walters has been a journalist for more than 60 years, spending all but a few of those years working for California newspapers. He began his professional career in 1960, at age 16, at the Humboldt Times...