LOS ANGELES — When Sen. Barbara Boxer announced on Jan. 8 that she would be retiring after her current term ends in 2016, Democrats in Southern California quietly rejoiced.

Sure, Boxer’s exit will be breaking “a generational logjam,” as the New York Times’ Adam Nagourney put it, “signal[ing] what many Democrats, especially younger ones, have been waiting for across this state: the beginning of a wave of retirement by an older generation of Democrats who have dominated the upper realms of elected office.”

But SoCal in particular had an even better reason to celebrate. Politically, Northern California has dominated Southern California for decades now — and Boxer’s departure was widely seen as a chance to finally tilt the balance of power back toward the lower half of the state.

Consider the numbers. Two-thirds of California’s nearly 40 million inhabitants live in the Los Angeles-San Diego corridor. Los Angeles is America’s second most populous city, with 3 million more residents than San Francisco. And the GDP of greater Los Angeles dwarfs the GDPs of San Francisco and Silicon Valley combined.

Yet for the last quarter-century, both of the Golden State’s U.S. senators have been from the Bay Area. As of 2015, seven of California’s nine statewide elected officials — Sen. Boxer, Sen. Dianne Feinstein, Gov. Jerry Brown, Lt. Gov. Gavin Newsom, Attorney General Kamala Harris, Controller Betty Yee, and Insurance Commissioner Dave Jones — call Northern California home. The other two, Secretary of State Alex Padilla and Treasurer John Chiang, are from Los Angeles, but they never had to run against rivals from the north.

Hence the excitement that greeted Boxer’s big announcement.

“I love San Francisco, but California’s population is disproportionately down here,” says Santa Monica-based consultant Garry South, who has advised Newsom and former Los Angeles Mayor Antonio Villaraigosa, among others. “A huge amount of economic activity is down here. And one of the things people down here feel strongly about is that having two senators from San Francisco for 24 straight years is not fair. It’s time for some people from the south.”

But now, four months after Boxer’s announcement, history already seems to be repeating itself.

The first candidate to enter the 2016 Senate race — Harris, the state’s attorney general — is as Bay Area as they come: born in Oakland, educated at San Francisco’s UC-Hastings Law School, groomed in the district attorney offices of Alameda County and San Francisco. She even dated former California Assembly Speaker and San Francisco Mayor Willie Brown. As soon as Harris launched her bid — less than a week after Boxer bowed out — the endorsements and money began pouring in. The word “front-runner” has been affixed to her name ever since.

SoCal has struggled to respond. L.A. Mayor Eric Garcetti ruled himself out before the press could even ask if he was running. Villaraigosa, his predecessor, spent six weeks publicly mulling a bid, then demurred. “I know that my heart and my family are here in California,” Villaraigosa said in February. “Not Washington, D.C.”

So far, the only serious Southern California Democrat to step up and challenge Harris has been Rep. Loretta Sanchez, and after a disastrous first few days on the trail, “serious” is starting to seem like a stretch. First, a draft email about Sanchez’s forthcoming announcement leaked to the press, prompting her to frantically deny that her announcement was, in fact, forthcoming. Then she announced anyway. Three days later, Sanchez mimicked a Native American “war cry” at the state Democratic Party convention, apparently in a joking attempt to differentiate between Native Americans and Indian-Americans. The subsequent controversy has, according to Roll Call, left Southern California Democrats “hesitant about whether they will back her uphill battle” against Harris.

Harris’ early dominance — and Sanchez’s early stumbles — raise larger questions about the politics of the country’s most populous, and perhaps most influential, state. Why does Northern California continue to wield such disproportionate power? What are the consequences of this imbalance? And can the current dynamic ever change?

“Sanchez isn’t the underdog because she says silly things,” explains Dan Schnur, who was a spokesman for former California Gov. Pete Wilson and Arizona Sen. John McCain and who currently teaches politics at the University of Southern California. “The story goes much deeper than that.”

It starts with geography.

San Francisco is, for all intents and purposes, a 19th century city. It’s situated on a peninsula, “a natural place for a city to be,” says University of California, Berkeley historical geographer Gray Brechin, author of “Imperial San Francisco.” It’s densely packed — “the only city on the West Coast with row houses like Boston or Philadelphia.” And because proximity breeds familiarity, “San Francisco has a culture, historically, of community- and neighborhood-based activism that goes back long before the 1960s.” For the same reasons, it also has a long history of political machines — what Brechin calls “Tammany Hall West.”

Los Angeles doesn’t. It’s far too 20th century for that: a vast, varied, multipolar metropolis that has been called “ less a conscious city than a series of alternatives;” a 500-square-mile agglomeration of disparate communities that only sprawled into one another after the postwar boom and the spread of the freeways.

For that reason, no Los Angeles pol has ever been able to do what San Francisco Congressman Phil Burton did in the 1960s : build a machine that eventually helped launch the careers of some of the most enduring names in California politics, from Willie Brown to Dianne Feinstein to Kamala Harris.

“It’s like the Daley machine in Chicago,” explains Brechin. “It just keeps going and electing the people that it anoints.”

This wasn’t as much of a problem for the South when California still had a viable GOP — almost every prominent Golden State Republican, from Ronald Reagan to Arnold Schwarzenegger, has come from Los Angeles, Orange County or San Diego. But as the Republican Party has shriveled in recent years, the Bay Area has gone from dominating Democratic politics to dominating California politics in general.

As a result, politicians from the Bay Area, and particularly San Francisco, often end up better prepared than their southern counterparts to endure challenging (and costly) statewide races.

“The political infrastructure in Northern California is more established, and because of that, Northern Californians seem able to elevate more people to higher office,” says San Francisco-based Democratic consultant Chris Lehane, a veteran of the Clinton White House and former spokesman for Al Gore. “People with real talent, like Kamala, are identified early on. They can rise through the ranks and develop relationships. That’s how she’s put herself in such an incredibly strong position.”

But candidates only represent one side of California’s imbalanced North-South equation; voters play an important part as well. And the problem for the South is that voters here tend not to vote.

The reasons are fairly clear. Bay Area residents are wealthier than ever, thanks to the recent tech boom. They are better educated. They identify more strongly with their region. And they are, in general, more informed about the issues.

In contrast, Southern Californians — many of whom are recent immigrants from Asia and Latin American — are less educated, less wealthy and less engaged with politics, which is much harder to follow in a massive metropolitan area made up of 88 incorporated cities.

“It’s kind of a standing joke among those of us in the consulting corps on both sides of the aisle,” says South. “You conduct focus groups in the Bay Area, and you almost always have better informed voters than you get in the L.A. focus groups. You run into people who’ve actually read the op-eds; in L.A., people don’t know which day it is, let alone who’s in the governor’s race. We’ll sit in the viewing room, and sometimes the moderator will have to knock on the window because we’re back there laughing at how uninformed they are.”

The turnout statistics are startling. There are 3.4 million registered voters in the Bay Area; Los Angeles County has 4.8 million. But last November, 1.7 million ballots were cast in the Bay Area, compared to 1.5 million in Los Angeles. Only 31 percent of registered Angelenos even bothered to vote. Los Angeles County also ranks “dead last” in the state for voting by mail, as the Sacramento Bee’s Dan Morain recently reported.

This disparity has a real effect on Election Day. South points to the 2014 state controller race between former Speaker of the Assembly John Perez (an Angeleno) and Board of Equalization member Betty Yee (a San Franciscan) as a “perfect example of why a candidate from the Bay Area has an automatic advantage over someone running from L.A. County.”

“Perez has all this power as speaker,” South says. “He commands lots of money and endorsements — he gets almost all of them. Everyone thinks he’ll knock Yee out of the box relatively easily. And yet she beats him, just barely, because she cleans his clock in the Bay Area — and more people vote there, even though a lot fewer people actually live there.”

What happened to Perez should frighten Sanchez. He was the front-runner, but he lost all the same. She’s just the underdog.

Yet some observers believe that given the right conditions and the right candidates, 2016 could mark a turning point in the rivalry between Northern and Southern California.

The reason? Demographics.

California is now a majority-minority state. Latinos outnumber non-Latino whites, and most Latinos live in the south, where their ranks are rapidly growing. Los Angeles County is 48 percent Latino at this point. In San Francisco, that number is only 15 percent.

In 2016 — a presidential election year — low-propensity voters (like Latinos) will already be flocking to the polls in greater numbers than usual; the fact that an open Senate seat is at stake for the first time since 1992 will help as well. A strong Latino candidate from Southern California could further expand the electorate, or so the thinking goes.

When Villaraigosa was mulling a Senate bid earlier this year, South provided him with a private polling report that showed how his presence in the 2001, 2005 and 2009 Los Angeles mayoral races produced spikes in Latino turnout. In the 2001 mayoral primary, for example, the Latino share of the electorate (21 percent) matched the Latino registration rate (21 percent) for the first time on record; in 2005, Latinos made up 26 percent of the electorate, exceeding their registration rate by 4 percentage points.

Call it the Sleeping Giant Theory. “There is the potential for a high-profile, credible Latino candidate, who is not just a gadfly with no record, to increase Latino turnout here in Southern California,” insists South. “No doubt about it.”

Whether Sanchez can become that candidate remains to be seen. There is a reason, after all, why one of Sanchez’s House colleagues, Rep. Xavier Becerra of downtown Los Angeles, is continuing to eye the 2016 contest. Becerra (who is also Latino) has said that he will make a decision by the time Congress breaks for August recess; at the Democratic convention last weekend, he was reportedly asking activists to refrain from supporting other candidates until then.

Ultimately, some believe that Northern California’s dominance may be coming to an end — whatever happens in 2016.

“Northern California has been predominant statewide on the Democratic side in no small part because it has had a much larger percentage of the Democratic vote share in Democratic primaries,” says Lehane. But in 2012, the state instituted an open-primary system that pits the top two finishers against each other in a fall runoff, regardless of party, so “that is changing,” Lehane continues. “With the explosion of the Latino population as well, you’re beginning to see a little bit of an evolution in terms of relative political strength.”

One clear sign of that evolution, Lehane argues, is the recent rise of Southern Californians in the state legislature. “For the first time in a long time, both the speaker and the head of the Senate are from Southern California,” he says. “Toni Atkins is from San Diego. Kevin de Leon is from Los Angeles. In particular, de Leon represents one of the leaders of the next generation. He’s a young politician who will be around for next 20, 30 years. He’s already one of three, four, five most impactful people in the state. And historically, these guys in the statehouse eventually run statewide.”

So take heart, SoCal. Sanchez may come up short next November. Becerra might not be able to defeat Harris. But Jerry Brown is retiring in 2018. Feinstein might retire then as well. And two years isn’t all that long to wait for a rematch.