- The 40th Senate District is one of the few remaining true toss-ups in California, but the trendline favors Democrats. Republicans' registration advantage has collapsed from 14.3% in 2014 to near parity, and their turnout edge has shrunk from 21.6% to just 1.3%.
- Kristie Bruce-Lane likely enters the Republican primary with a structural name ID advantage over Ed Musgrove, having run four times across primaries and generals in a geography that covers 46% of the Senate district — but her past general election underperformance of roughly 2.3% is a liability in a seat decided by single digits.
- The most consequential decision in this race may not be made by voters but by outside spenders, who must weigh whether shaping the Republican nominee is worth the cost of a bruising primary — or whether preserving resources for a difficult general election is the smarter bet.
The upcoming race for the 40th Senate District could be among the closest elections for Senate in the state. The 40th, which covers a large chunk of central San Diego County, is the only Senate district that both Brian Dahle and Kamala Harris won. In addition, voter registration is nearly even, making this a true toss-up.
This analysis will rely heavily on data from The Ballot Book’s unique database of political data. It offers a clear example of how data can better help us understand elections and allow political professionals to make more informed decisions.
The 40th District
To illuminate the swing characteristics of this district, it went for Republican John Cox by 6% in 2018, Democrat Joe Biden by 6.1% in 2020, Republican Brian Dahle by 5% in 2022, and Democrat Kamala Harris by 3.8% in 2024. (These numbers are aggregated to the current district lines, despite two of these elections occurring prior to redistricting.)
In 2024, the total Congressional vote (across four districts) saw a D+1.6% advantage, whereas in 2022 that number was R+1.2%.
Proposition 50, meanwhile, won by 6.4%, indicating a potentially more favorable environment for Democrats heading into this cycle.
Like many districts in California, this is one that was once solidly Republican but has drifted into swing territory. In 2014, Republicans held a 14.3% registration advantage and a 21.6% turnout advantage in the general election. In 2024, registration was essentially even, and Republicans enjoyed a turnout advantage of just 1.3%.
The district is relatively conservative on taxes, having voted down most statewide tax measures and consistently ranking lower than other Senate districts in its support for bond measures.
Our recent post estimating Trump’s approval rating by district put his approval rating at 37.1% in the 40th District, ranking it the 14th most Trump-friendly district. In November, it ranked 11th in terms of raw Trump vote share.
Brian Jones, the termed-out incumbent, won by 6.2% in 2022 against Democrat Joseph Rocha.
Rocha was relatively unknown prior to the election but still managed to spend nearly $1.6 million across the primary and general election, falling just short of Jones’ $1.9 million. Jones, however, was the beneficiary of $200,000 in positive independent expenditure spending, whereas Rocha faced $140,000 in opposition spending.
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The Candidate Field
The candidate field has seen some turnover. Most notably, Marni von Wilpert, a San Diego City Councilmember, initially filed for the seat but later decided to run for the 48th Congressional District against Darrell Issa once the new lines emerged. After she bowed out, former San Diego City Attorney Mara Elliott entered the race.
Two Republicans have been in the race since near the beginning: San Marcos Councilmember Ed Musgrove and Kristie Bruce-Lane, a former local elected official who has run twice in highly contested Assembly races but fell short both times.
San Diego Unified trustee Sabrina Bazzo was initially a candidate but ultimately dropped out, as did Suzanne Till.
Here is where the candidates stand in terms of fundraising as of 12/31/2025:
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Mara Elliott
Elliott’s extensive name recognition in San Diego and record as a citywide elected official give her a strong base. While City Attorney isn’t necessarily the most prominent elected position in the city, she nonetheless played a meaningful role in local government and frequently drew media attention for issues such as gun violence prevention and consumer advocacy.
The City of San Diego makes up 33% of the Senate District, which gives her a solid foundation to run from, though it also leaves her relatively less known in other parts of the district.
As the only Democrat in the race, she should have a relatively easy primary and will be able to watch from the sidelines as her two Republican opponents battle one another.
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Kristie Bruce-Lane
Kristie Bruce-Lane is a former Olivenhain Municipal Water District board member and nonprofit founder. She previously ran for the 76th Assembly District twice — in 2022 against incumbent Brian Maienschein and again in 2024 in an open seat against Darshana Patel. In 2022, she lost by 3.2% to Maienschein and by 8% to Patel in 2024.
During the 2022 primary, she prevailed over another strong Republican challenger, June Cutter, who had actually outraised Bruce-Lane in that contest. Based on precinct analysis of that race, the vote in more Republican precincts was most strongly correlated with Bruce-Lane, allowing her to prevail over Cutter.
As a result of her two races, Bruce-Lane likely enters the 2026 Senate race with a reservoir of name ID. The 76th Assembly District comprises 46% of the 40th Senate District. In her 2024 race against Patel, Bruce-Lane spent more than $1.6 million and benefited from $338,000 in independent expenditures supporting her (alongside $135,000 in opposition), and she spent more than $700,000 in her 2022 defeat against Maienschein.
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Ed Musgrove
Ed Musgrove is a current San Marcos City Councilmember (representing District 4), a U.S. Army veteran, and a retired Sheriff’s Department captain. In his first election in 2020, he won by a 14.2% margin and won re-election in 2024 by a 29-point margin.
What makes those victories compelling is that he won in a district that went for Joe Biden by 11.1% in 2020 and for Harris by 6.6% in 2024. During the midterms, the district went for Brian Dahle by 3.4% and John Cox by 1.4%, mirroring the swing nature of the 40th Senate District.
Musgrove has shown the ability to convincingly win in a moderate district, which strengthens his case considerably for the 40th District. The issue for Musgrove is that, in contrast to Bruce-Lane, his council district makes up just 2.4% of the Senate District, likely creating a name ID deficit relative to Bruce-Lane.
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Endorsements
In terms of the endorsement landscape, Musgrove has cobbled together a strong coalition of institutional endorsements, including outgoing Senator Brian Jones, Congressman Darrell Issa, several other legislators and local elected officials, as well as public safety organizations and a handful of local tribes.
Bruce-Lane, by contrast, has fewer notable endorsements within the district but does have the endorsement of Carl DeMaio and Reform California. That endorsement carries additional value, as 39% of the 40th Senate District overlaps with the 75th Assembly District, which DeMaio represents. Should he decide to weigh in heavily in this race, his name could carry more weight here than in other geographies due to his local ties.
As the only major Democrat in the race, Elliott has already secured a notable number of endorsements from Democratic elected officials and aligned organizations.
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Primary Analysis
As far as the primary is concerned, the election is effectively about determining which Republican comes in second place to take on Elliott in the general election.
Upon first glance, Musgrove appears to be a strong candidate to fill that second slot. He’s leading the money race so far and has secured endorsements that tend to resonate well with Republican voters.
The potential problem for Musgrove is the size of the district. More than 200,000 voters showed up in the last two midterm primaries in 2022 and 2018. In each of those elections, more than 90,000 Republicans voted. When you consider that a large portion of those voters have cast ballots for Kristie Bruce-Lane — some of them as many as four times across primaries and general elections — it’s more likely than not that Musgrove is starting from behind.
It’s also worth noting that some of Bruce-Lane’s endorsements come from more conservative voices, such as Carl DeMaio, gubernatorial candidate Chad Bianco, and the San Diego County Gun Owners PAC. While these endorsements have varying levels of familiarity among Republican voters, they nonetheless signal a candidate drawing support from the more conservative wing of the party.
That dynamic could be compounded in a primary electorate, where more moderate voters often get squeezed out and turnout skews more conservative. That structural reality likely works to Bruce-Lane’s advantage.
Accordingly, despite his strengths, Musgrove faces a structural disadvantage. It’s certainly not insurmountable with the right campaign, but at this point, it may be preferable to be Bruce-Lane than Musgrove.
An X-factor in the race could be whether outside groups decide to weigh in and support Musgrove, which may require running negative ads against Bruce-Lane to tamp down her existing support base. For those considering spending money, that raises important strategic questions.
First and foremost, whether it’s Musgrove or Bruce-Lane who emerges from the primary, there will still be a general election battle against a formidable Democrat in a challenging environment for Republicans. The key decision isn’t whether Musgrove would make a strong legislator, but whether Bruce-Lane is perceived as a risk to institutional stakeholders.
While DeMaio’s endorsement gives Bruce-Lane measurable upside within a defined segment of the Republican electorate, the implications extend beyond this race. From Sacramento’s perspective, the question is less about ideology and more about alignment. Bruce-Lane is not meaningfully outside the Republican mainstream, but her election would likely add another legislator aligned with DeMaio — a figure who has not been a favorite among Sacramento’s institutional interests and who was the subject of significant independent expenditure opposition in 2024.
That dynamic introduces a strategic timing question for outside groups. They can choose to engage early in the primary if they believe shaping the nominee matters to the broader balance of influence in Sacramento. Or they can allow the primary to resolve organically and preserve resources for the general election, where the seat itself is at risk in a challenging environment for Republicans. The calculus is not about ideological alarm, but about institutional positioning — and whether that justifies early intervention.
General Election
While the seat is definitionally a “swing” seat based on its recent propensity to vote for candidates of both parties at the top of the ticket, the district — like many others in California — has been trending more blue.
As I’ve written previously, Republicans face strong headwinds heading into 2026. Trump is radioactive in California, and the 40th Senate District is full of the higher-education, higher-income voters who have moved heavily against the President and the Republican Party over the past several cycles. As mentioned earlier, our estimates of Trump’s approval rating by legislative district put his approval at just 37.1% in the 40th District.
Should Bruce-Lane be the Republican nominee, her past performance in general elections is not particularly encouraging. In a previous post, we examined which Assembly candidates most over- or underperformed relative to what would have been expected based on how their districts voted for partisan candidates (Governor, U.S. Senate, etc.). Bruce-Lane underperformed her district’s baseline by approximately 2.28%. That is only one data point, and it could just as easily be attributed to a strong opponent rather than any inherent weakness. Nonetheless, it is less than ideal in a district where margins are already thin.
Musgrove presents a more intriguing case. While his district was small and technically non-partisan, he still won both elections by double digits — each time with Trump at the top of the ticket. It is difficult to know how well that performance translates to a much larger, explicitly partisan race, but he has demonstrated the ability to win comfortably in swing territory. Whether that reflects personal brand, coalition-building, or local positioning is an open question — but it is not nothing.
The challenge for either Republican is that a competitive primary could force them to expend resources and potentially take positions that play well in June but are less optimal in November. That said, competitive primaries can also clarify contrast, sharpen messaging, and produce a more battle-tested nominee. There is downside risk, but there is also upside in the refining process.
Mara Elliott, by contrast, would enter the general election relatively unscathed and largely resource-intact. She has won twice citywide and was initially elected as a long-shot candidate. She is a credible Democratic recruit and is unlikely to face difficulty raising money between now and November.
As for her vulnerabilities, voters are not currently enamored with the City of San Diego, due to increases in various fees, reductions in services, and lingering frustrations from prior controversies. A Republican opponent will certainly attempt to tie Elliott to those dynamics. However, as City Attorney — rather than Mayor or Councilmember — and having left office before some of the most recent budget reductions took effect, she is somewhat insulated from direct blame. Moreover, most of this race will likely be framed around Sacramento and federal dynamics, making it difficult for hyper-local grievances to meaningfully reshape the electorate.
Conclusion
What makes the 40th difficult to handicap is not that it is unpredictable — it’s that it is elastic. The district will tolerate a Republican, but not just any Republican. It will tolerate a Democrat, but not one misaligned with its fiscal instincts. Small differences in candidate profile, tone, and geographic strength could matter far more here than in a safely red or blue seat.
For right-aligned donors and interest groups, the decision point comes early. Do they shape the primary to ensure the nominee they believe is best positioned in November, or do they allow the electorate to sort itself out and conserve resources for what will almost certainly be a tightly contested general? For Democrats, the calculus is simpler: unify early, define the Republican nominee, and let the broader political environment do some of the work.
In a district decided by mid-single digits at the top of the ticket — and where turnout advantages have narrowed from double digits to almost nothing — structural fundamentals will matter. But so will execution. This is the type of seat where a few thousand votes in the right precincts can outweigh ideology, endorsements, or even national mood.