election of 2020 included all of Stanislaus County (including Ceres, Oakdale, Modesto, Riverbank, and Turlock) and the southern portion of San Joaquin County (including Tracy and Manteca). This went into effect in 2012, as the result of redistricting by the California Citizens Redistricting Commission. This version of the 10th included much of the core of the old 18th district (Modesto, Ceres, and the southwestern half of Stanislaus County), though the 18th also included a substantial portion of Stockton. It also shares much of the northwestern portion of the old 19th district (Turlock, Riverbank, Oakdale, and the rest of northeastern Stanislaus County). Republican Jeff Denham transferred from the prior 19th district to the newer 10th. He held it for three terms until being defeated in 2018 by Democrat Josh Harder, who won reelection in 2020. After 2022 The 10th district was redrawn in time for the 2022 election, being divided up between California's 5th congressional district (which now includes eastern portions of Modesto and eastern portions of Turlock), California's 9th congressional district (which is centered on Stockton, California and includes Tracy), and California's 13th congressional district (which includes western Modesto and western Turlock) . Current 10th district incumbent Josh Harder is running for reelection in the new version of California's 9th congressional district. Election results from statewide races 1992 – 2022 Competitiveness Voter Registration Statistics The California Secretary of State publishes reports on California voter registration on a regular basis. Before the 2018 primary election, they published a report dating May 21, 2018. Composition As of the 2020 redistricting, California's 10th congressional district encompasses most of Contra Costa County, and part of Alameda County. Contra Costa County is split between this district, the 8th district, and the 9th district. The northern border is partitioned by Grizzly Peak Blvd, Seaview Trail, Camino Pablo, Bear Creek Rd, San Pablo Creek, Bear Creek, Brianes Reservoir, Burlington Northern Santa Fe, Highway 4, Alhambra Ave, Pacheco Blvd, Grandview Ave, Central Ave, Imhoff Dr, Bares Ave, Mount Diablo Creek, Union Pacific, Contra Costa Canal, 4WD Rd, Bailey Rd, James Donlon Blvd, Cambridge Dr, Reseda Way, S Royal links Cir, Carpinteria Dr, Barmouth Dr, Hillcrest Ave, Highway 4, and Highway 160. The western border is partitioned by Old River, Italian Slough, Western Farms Ranch Rd, Rankin Rd, Highway J14, Byron Hot Springs Rd, Camino Diablo, Kellogg Creek, Sellers Ave, Brentwood Blvd, Alloro Dr, Ghiggeri Dr, Emilio Dr, Guthrie