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The electoral map of San Diego County has changed dramatically in recent years, according to party registration.
The electoral map of San Diego County has changed dramatically in recent years, according to party registration.

How San Diego's political map shifted from red to blue and what comes next

Take a look at a San Diego County voter registration map and you'll see a county that has become quite a bit more blue over the past two decades. Then talk to some voters who’ve left the Republican Party and they'll have no problem telling you why.

For Mountain View resident Joel Ryan, it was the Republican Party’s embrace of the anti-gay marriage Proposition 8 in 2008.

For Bonita resident Niki Petzoldt, it was Donald Trump’s campaign for president in 2016.

Get general information about the election, news coverage, an interactive ballot guide, and results on election day.

For Sorrento Valley resident Steve Harris, it was the Jan. 6 Capitol insurrection and what he saw as a failure of Republican leaders to condemn it.

These San Diego County residents are part of a political shift seen in voter registration data between 2004 and 2020. The shift, which started slow and picked up steam in recent election cycles, has transformed San Diego from a reliably red county to the light blue county it is today.

San Diego General Election Registration History, 2004-2020

In 2004, when George W. Bush won reelection, 42% of voters in San Diego County were registered Republicans, 35% were Democrats and 19% no party preference. In 2020, when President Joe Biden was elected, the county was 42% Democrat, 29% Republican and 24% no party preference.

The impacts of this sea change have been significant.

“We've seen this radical transformation just over the last two decades in San Diego from really a Republican stronghold to a battleground and now to an area where if you look at the county Board of Supervisors, the City Council, the legislative coalitions, Democrats have almost locked up every position,” said Thad Kousser, a politics professor at UC San Diego.


Yet, this shift has not happened evenly across the county. Areas like Escondido, Carlsbad, Lake San Marcos and Valley Center all saw a big drop registered Republicans between 2004 and 2020. But GOP registration actually increased in other places, like El Cajon and Encinitas.

Why voters switched

Petzoldt said she grew up in a small “very conservative” town and was always a Republican. But as she watched the 2016 presidential campaign she became more interested in politics and was turned off by Trump.

That election “started me reading, researching, being involved, and I just did not align with anything that they were doing,” she said of the Republican Party under Trump. “By the time it came time to vote in 2020, there was just absolutely no way I could vote for another Republican ever.”

Petzoldt, who works as a nurse serving low-income families, said her views on healthcare are now far more aligned with the Democratic agenda.

“I see what lack of access does,” she said. “By the time they get into the hospital, it's because they couldn't afford medical care up until that point. They couldn't manage their diabetes. They couldn't manage their high blood pressure, and now they're in the hospital getting an amputation or with a stroke.”

Petzoldt said she now votes the entire Democratic ticket — ”the entire ticket, even if I didn't know what the office was” — and while she still needs to do more research on some candidates and measures, she doesn’t think she’ll ever vote for a Republican again.

This doesn't surprise Kousser, who said California Republicans were always more moderate. That includes politicians like Congressman Brian Bilbray and Governor Arnold Schwarzenegger, who were socially liberal and pro-environment but fiscally conservative.

“And that's not Donald Trump,” Kousser said. “The culture wars, getting rid of reproductive choice through Roe v. Wade and pulling out of the Paris climate accords, those sorts of steps took the Republican Party sharply to the right and really too far to the right for many San Diego Republicans.”

But Trump supporters aren't hard to find in the county. Coronado resident Mary Scyocurka is a lifelong Republican and backs Trump. Though she doesn’t like everything the former president has said, she thinks his policies were successful.

“You don't always have to like the person in charge of a company, but if they're running things, well, then they have my support,” she said.

Scyocurka said the region is turning bluer because of people leaving California and older Republican voters dying off and being replaced by younger voters. That makes her concerned about the future of the county.

Jordan Gascon, the executive director of the San Diego Republican Party, said he and other local party leaders need to find common ground.

“People just cannot separate national politics from local politics,” Gascon said. “Unfortunately, we had a divisive president, and there are a lot of people that really like him and follow and support him. And then there are other Republicans that maybe did not necessarily like the personality but like the policies and have separated themselves.”

The rise of no party preference voters

The data do not show all the voters fleeing today’s GOP are flocking to the Democrats. In fact, the county's share of registered Democrats only jumped from 35% in 2004 to 42% in 2020, hardly a blue wave.

The segment of voters that has grown the most are no party preference voters. They are often moderates who don’t like Trump's Republican Party, but also don’t feel at home in a Democratic Party that has tilted left in recent years.

Harris, the former Republican from Sorrento Valley, fits this mold. He said he doesn’t vote for any Republicans at the federal level, but does vote for Republicans for state office because “California needs more balance.” He weighs local candidates on what they’re promising and what they’ve accomplished.

Ryan Clumpner, a San Diego-based campaign consultant, said this is the new reality campaigns must contend with in local elections.

“In the 2000s, independents had a very particular set of behaviors, they were a little bit more irritable about campaigns in general,” Clumpner said. “So for example if you were knocking on doors for a campaign, they notoriously did not want to hear from you.”

Independent voters also used to be older, he said, but now they skew younger and can be quite politically engaged.

“Their affiliation as an independent is actually a reflection that they hold very specific opinions about politics, rather than that they don't want to be bothered with politics,” Clumpner said.

Gascon said he tells voters to stay in the party and change it from within.

How San Diego's political map shifted from red to blue and what comes next

“You have these giant engines on both sides of the aisle that can be influenced by the individuals that are involved," he said. "So staying Republican and moving the Republican Party in the direction that you want to see it I think is very important. And people should stay in the Republican Party to do that, to effect change.”

The impact of growth patterns

It would also be a mistake to settle on simple explanations for the shift in San Diego’s electoral map, Clumpner said. The region’s demographics and growth patterns play a significant role.

For example, areas like Mira Mesa and Mission Valley have built more dense housing in the past decade, which draws in residents who are more likely to be lower income and younger. Those voters are less likely to be Republican, he said.

“That changes the issues that they care about and how they live their lives, like their access to public transit, the proximity to jobs, how close they are to their neighbors,” Clumper said. “In a different environment, the same voters might be behaving in a different way because they would care about different issues.”

Clumpner also points to how the shift from red to blue has largely been driven by voters in northern coastal areas. Since 2004, Carlsbad, La Jolla, Del Mar, Oceanside and Rancho Santa Fe have all seen drops in Republican registrations.

“They have always been more moderate areas, but I think issues like climate change and in particular the Trump era and how polarizing it was really pushed those areas to be much more staunchly Democratic than they were before,” he said.

However, he said, those areas can still skew conservative on local issues concerning housing and transportation.

Meanwhile, Kousser said local politics can be like the weather—if you don’t like it, just wait awhile and it will change.

“I don't think those numbers just keep going in the same trajectory forever," he said. "I think San Diego Republicans will be looking for the candidates who can speak across party lines, who can be attractive to independent voters. If they do that, that is a path back towards relevance for the GOP in San Diego.”

As deputy investigations team and digital fellowship editor, Claire helps lead the investigations team and digital-first content like podcasts, YouTube videos and data visualizations. She works collaboratively with the news team to produce and enhance investigative and enterprising stories.
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