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City of Diamond Bar · Statewide General Election

Diamond Bar City Council, District 4

Draft candidate list — early preview until the state’s official list publishes on August 27, 2026.

This is one contest. Enter your address to see every race on your November ballot, and keep track of your picks.

On the ballot

This person holds your district's seat on Diamond Bar's 5-member City Council: city ordinances, the budget, and land use.

Incumbent Chia Yu Teng, a physician and the council's mayor since December 2024, faces a rematch against Lee Mao, a small-business owner who lost to Teng by fewer than 40 votes in 2022, for the District 4 seat.

This person holds one of five district seats on Diamond Bar's City Council: city ordinances, the budget, and land-use decisions. A 4-year term. Council members choose one of their own to serve as mayor and mayor pro tem, presiding over meetings but casting only one vote like any other member.

Teng is campaigning on continuing to prioritize economic development for small businesses and public safety, drawing on a current term as mayor. Mao, in his second run for the seat after the narrow 2022 loss, is campaigning on fiscal responsibility without new taxes, public safety, traffic reduction, and expanding recreation — drawing on his own service as Vice-Chair of the city's Planning Commission.

Chia Yu Teng

Chia Yu Teng is the incumbent, elected in 2022 and selected by the council to serve as mayor starting December 2024. Teng holds a doctorate in chemistry from Cornell and an M.D. from the University of Miami, has practiced medicine for more than 30 years, and in 2004 co-founded Central Health Plan of California, a Diamond Bar healthcare organization. Teng's stated council priorities are economic development for small businesses and public safety.

Strengths

A current term as mayor plus a 30-year medical career and co-founding a regional healthcare organization bring administrative experience beyond the council itself.

Trade-offs

Won the 2022 race by fewer than 40 votes out of roughly 2,500 cast — one of the closest margins among this cycle's incumbents, meaning the district split nearly evenly last time.

Keep in mind

Teng's own campaign committee has no itemized contribution on file this cycle, only two itemized payments — see Financial info.

Lee Mao

Lee Mao immigrated from Taiwan at age 10, moved to Diamond Bar in 1993, and started a bedding business in 1996 that he has run online since 2000. He currently serves as Vice-Chair of the city's Planning Commission and on its Parks and Recreation Commission. He's making his second run for the District 4 seat after narrowly losing to Teng in 2022, and has said publicly that recent, unrelated federal scrutiny of some Chinese American community figures has not changed his decision to run.

Strengths

Sitting Vice-Chair of the Planning Commission gives him direct land-use experience, and a second run means voters have a prior record to weigh against this year's platform.

Trade-offs

Lost the 2022 race by fewer than 40 votes — the closest margin of any Diamond Bar council race on record for this cycle's incumbents.

Keep in mind

His campaign has no itemized contributions or payments on file at all this cycle, only routine candidacy paperwork — see Financial info.

Source review: Strong (84/100) · 6 cited sources

Official records anchor this contest, with several source types checked for context; advocacy or endorsement sources are treated as attributed perspective.

Review note: Lee Mao for Diamond Bar City Council 2026 may have more bias because it is an advocacy voter guide compared to other formal government and nonprofit journalism sources.

  • diamondbarca.gov (opens in a new tab)City of Diamond Bar — Election Information (City Clerk's qualified-candidate list for City Council Districts 1, 3, and 4, with Form 501 and nomination-paper filing dates)
  • netfile.com (opens in a new tab)City of Diamond Bar — NetFile Public Portal (campaign committees and itemized campaign-finance transactions for all 2026 candidates, searchable inline without a document download)
  • diamondbarca.gov (opens in a new tab)City of Diamond Bar — Council Member Chia Yu Teng (official council-member bio: District 4, term as mayor, occupation, committee roles)
  • lee4diamondbar.com (opens in a new tab)Lee Mao for Diamond Bar City Council 2026 — campaign site ("Meet Lee Mao")
  • dailybulletin.com (opens in a new tab)Daily Bulletin (Southern California News Group) — "Chinese American leaders fear 'collective suspicion' after LA, San Bernardino county FBI searches" (quotes Lee Mao on his 2026 candidacy and his narrow 2022 loss)
  • rafu.com (opens in a new tab)Rafu Shimpo — "Results for Asian American Candidates in L.A. County Municipal Races" (Nov. 19, 2022; certified-adjacent District 4 results, Teng 1,301 to Mao 1,266)

Last updated August 31, 2026.