Author’s Note: Other 2026 forecasts can be found in the Central File. This forecast/prediction contains proprietary mapping data beyond the paywall information prepared by the author for analytical purposes.
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I. The Race
Jim Desmond (Republican) has served two terms on the San Diego County Board of Supervisors. He’s a Navy veteran and is focusing his campaign on ensuring borders remain secure and policing crime and drug activity, which is rampant in urban California.
Marni von Wilpert (Democrat) is essentially the reverse image of Desmond. She’s a member of the San Diego City Council, and runs the standard female “get Trump” campaign focused on vague positions like healthcare and affordability, and more nefarious efforts to handcuff ICE and restrain them from fixing the city she’s helped ruin.
II. District Geography
California’s 48th Congressional District (CA-48) is newly drawn and facing the first election held under its new boundaries. The current CA-48 is held by Darrell Issa (Republican), who won by 18.6% in 2024 and is retiring instead of dealing with the new boundaries.
The new lines dodge conservative areas in northern San Diego County and run northeast in Riverside County to include Palm Springs, a hippie Democrat stronghold with huge margins. President Trump made a lot of progress within these boundaries in 2024, but still fell short against Kamala Harris.
Presidential Margins
Key Statistics
53.3% White, 29.4% Hispanic, 6.9% Asian
III. Market Assessment
Polymarket bettors are sticking with the California Democrat home team and expecting their all-mail elections to get von Wilpert over the top.
IV. History
There is no precedent for swing and election outcomes in the district as it will be drawn for this election; however, in the first Trump midterm including Palm Springs (then in CA-36), the swing favored the GOP from 2016, swinging right by 6.2%. Raul Ruiz had won in 2016 by 24.2%.
Still, most of the swing in margin came from outlying areas of the district, which stretched east to west across California and deep into the desert.
V. Analysis of 2026 Primary Results