When California Sen. Barbara BoxerBarbara Levy BoxerFirst senator formally endorses Bass in LA mayoral bid Bass receives endorsement from EMILY's List Bass gets mayoral endorsement from former California senator MORE (D) announced that she wouldn’t seek a fifth term next year, she did more than create a job opening in Washington.

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For openers, Boxer brought the Golden State out of a state of suspended animation. The last time California held an open-seat contest for the U.S. Senate was all the way back in 1992 — before there was a Clinton presidency, Viagra (not that the two are related), iPods, iPads and Google eyeglass.

Second, in a state dominated by Democrats and their coastal-blue progressive sensibilities, Boxer potentially set in motion a rift within her party in 2016, with battle lines drawn by race, gender and geography.

About California's Senate primary: At present, it shapes up as a downsized version of the Democrats' presidential selection process. The one announced candidate on the Democratic side — state Attorney General Kamala HarrisKamala HarrisJoe Manchin should embrace paid leave — now The Hill's 12:30 Report: Biden defends disappointing jobs report Harris's office undergoes difficult reset MORE — dominates. Absent any prominent Democrats challenging her, Harris's candidacy would have all the airs of a coronation (among Harris's first endorsers: Massachusetts Sen. Elizabeth Warren (D), maybe the one person standing between Hillary Clinton and the prize that eluded her in 2008).

However, that changes if former Los Angeles Mayor Antonio Villaraigosa (D) enters the contest. If so, then the Senate primary tugs at the heart of the Democratic existence in California.

And Republicans? As the minority party hoping for a top-two finish in the June open primary and thus a spot on the November ballot, the GOP's hopes rest on the more the merrier — two or more Democrats diluting the left's share of the vote, with a small number of Republican hopefuls splitting their share.

That, and a couple of heavyweights who could turn the open primary into a wide-open brawl.

In Harris, Democrats have a candidate who's not only a woman, but one of mixed racial identity (African-American father, Asian-American mother) who comes from the same San Francisco Bay Area power teat as Boxer, Sen. Dianne FeinsteinDianne Emiel FeinsteinWhat's that you smell in the Supreme Court? New variant raises questions about air travel mandates Progressive groups urge Feinstein to back filibuster carve out for voting rights or resign MORE (D), Gov. Jerry Brown (D) and House Minority Leader Nancy Pelosi (D) and is on cozy terms with the Obama White House (the president once calling her "the best-looking attorney general in the country").

In the other corner, Villaraigosa: male, Latino, from dollar- and vote-rich Los Angeles. And not on great terms with the White House (after chairing the 2012 Democratic National Convention, Villaraigosa lobbied like crazy to become the nation's Transportation secretary, only to take himself out of the running — not long after Charlie Sheen had bragged about partying with the mayor in Cabo San Lucas).

A word of caution about a Villaraigosa candidacy. Yes, it's a compelling narrative should he attempt to become the state's first Latino senator (at present, only one Latino holds statewide office in California: Democratic Secretary of State Alex Padilla). And, yes, the Latino vote — representing nearly one in five likely California voters, nearly triple the number of black voters — is a sleeping giant.

Unfortunately for Villaraigosa, that same sleeping giant tends to catch 40 winks come election-time, with the Latino turnout underperforming in most California votes. Moreover, in California primaries, Latinos tend to turn out stronger in such pockets as the Central Valley and Silicon Valley's Santa Clara Valley, which are well beyond Villaraigosa's L.A. base.

One other challenge facing Villaraigosa, who left office back in 2013 due to term limits: being a Los Angeles mayor is the kiss of death for statewide aspirations. Tom Bradley ran for governor twice in the 1980s and failed, as did fellow Democrat Sam Yorty in 1966, 1970 and 1974 (Yorty also sought the presidency in 1972). Richard Riordan, a Republican, gave it a go in 2002 and couldn't survive the partisan primary. The closest thing to a happy ending in Hollywood is Williams Stephens, who served for a week as L.A.'s acting mayor in March 1909 before going on to become California's governor eight years later.

That leaves the nation's largest state with the distinct likelihood of Harris as its next senator (no Republican has won a Senate race since Pete Wilson in 1988, which is also the last time California went with the GOP in a presidential election).

But what Californians would actually get is anyone's guess.

Judging by the vague and cliche announcement on her campaign's website, Harris sounds a lot like Hillary Clinton six months from now ("a fighter for middle-class families who are feeling the pinch of stagnant wages and diminishing opportunities"). By using a variation of "fight" no less than seven times in that six-paragraph statement, she's channeling the notoriously pugnacious Boxer.

What Harris is, in fact, is a California equivalent of President Obama: little in the way of a record in her political career as attorney general and Bay Area prosecutor, but riding a tailwind that's more conceptual than it is concrete. The Los Angeles Times said it best in an editorial endorsing her reelection last fall, describing Harris as "a work in progress, with much potential yet unfilled."

Such would seem California's political destiny for the near future. With two more plum jobs opening up in 2018 — governor and another Senate seat — the potential exists for two more primaries in which Democrats will clash. Two things we know about the next class: They'll be younger (Brown is America's oldest governor; Feinstein the Senate's oldest member). And they'll be more progressive and idealistic than the aforementioned incumbents, who've built reputations of pragmatism and moderation.

Done in an orderly fashion, California Democrats can sort out their business in an orderly fashion. But the more crowded the primary, the greater the potential to divide the coalition.

And Kamala Harris? Consider this one last Obama parallel: an easy Senate victory and, should her party lose the presidency, a spot on the national ticket after only four years in Washington.

Whalen is a Hoover Institution research fellow. His blog, A Day At The Races, follows California and national politics.