Each week, the San Bernardino County elections office publishes updated voter registration data not only for the county but also for all of its local entities, one being the City of Rancho Cucamonga.

The Oct. 1 weekly report contained an interesting bit of data about the city—that the longtime Republican stronghold now leans Democratic by 33 registered voters.

It’s a tiny indicator of the GOP’s continuing slide into political irrelevance, the more poignant because the party’s current state chairman, Jim Brulte, called Rancho Cucamonga home when he represented the region in the state Legislature.

From its heyday in the 1980s and early 1990s, when the GOP was at virtual parity with Democrats and semi-dominant in statewide elections, Republicans have slipped to having no statewide officeholders and fewer than a third of the state’s legislative and congressional seats.

In just the last decade, Republican voter registration has declined from 34.2 percent of registered voters—still enough to make a difference—to 25.9 percent and by 2020 could fall into third place behind voters with no party preference, now 24.5 percent.

It is a truly remarkable, even historic, turn of events, especially in light of huge Republican gains in dozens of other states, reflected in the GOP control of both houses of Congress, 33 governorships and both legislative houses in 32 states.

Why it happened is the subject of endless speculation and debate in political and media circles. It’s some combination of demographic change—especially the relative decline of the state’s white population—and attitudinal evolution away from the GOP on such hot-button issues as gun control, abortion, same-sex marriage and climate change.

Whatever its antecedents, it’s a fact of political life, and Republican Party leaders don’t seem to know how to arrest the fall.

Their internal debate is reminiscent of the angst in the national GOP during the post-World War II era, pitting hard-line conservatives such as Robert Taft and California’s William Knowland against “modern Republicans” personified by Thomas Dewey and later Dwight Eisenhower.

Just as that era’s right-wingers refused to retreat from their isolationist leanings, so California’s never-say-die conservatives reject anyone who strays from their rigid positions on taxes and other issues. It’s their version of the “better-dead-than-red” mantra their 1950s predecessors chanted.

The split was very evident during the governorship of Arnold Schwarzenegger, who was often denounced by true believers to his right as a “Republican in name only,” or RINO.

It’s evident today in drives to push two young former GOP leaders of the state Assembly into political exile.

Chad Mayes was forced to step down from his leadership position after he broke party ranks and backed Gov. Jerry Brown on reauthorization of the state’s cap-and-trade system of reducing carbon dioxide emissions.

A few months later, Mayes’ predecessor as GOP leader, Stanislaus County Supervisor Kristin Olsen, resigned as Brulte’s party vice chair rather than face a pending GOP convention resolution demanding her resignation.

Among other things, her critics were waving a letter from Olsen’s estranged husband to the Assembly, asking for an investigation into whether any state funds were used to conceal a romantic relationship between Mayes and Olsen. An investigation never happened.

It’s common for dominant political parties to fragment into competing factions, but one would think that a party in steep decline would close ranks. Instead, the California GOP has devolved into a circular firing squad.