Incumbent Ed Case (D) defeated Jarrett Keohokalole (D) and three other candidates in the Democratic primary for Hawaii's 1st Congressional District on August 8, 2026. The filing deadline was June 2, 2026. As of May 2026, Case and Keohokalole led in fundraising and local media attention.

Spectrum Local News' Michael Tsai said, "While it is relatively rare for an incumbent of Case’s standing to face significant opposition in the primary, Case has drawn fire from within his own party for voting in support of Republican initiatives, including ... the so-called SAVE Act, which requires documented proof of citizenship to register to vote." In the 2024 primary, Case defeated Cecil Hale (D) 92.0%–8.0%.

Case was first elected to the U.S. House in 2002. He ran unsuccessfully for the U.S. Senate in 2006 and was re-elected to the House in 2018. Case's campaign website said, "Our country and world face immense challenges that demand strong, smart leadership to defend our democracy and deliver real solutions. ... If re-elected, I will move to the top 25% of House seniority, continue on the powerful Appropriations Committee, and further expand my relationships and influence."

Keohokalole was elected to the Hawaii Senate in 2018. He was a member of the Hawaii House of Representatives from 2014 to 2018 and earlier worked as a legal fellow at the Hawaii Department of Land & Natural Resources. In a campaign ad, Keohokalole said, "The solutions we've been getting from Ed Case are not good enough. Families like mine are being priced out of our communities. Our kids have to leave to build a future and the help we need, the urgency we deserve, is missing."

Also running in the primary were Jennifer Booker (D), Ben Fatula (D), and Nicholas Kiswanto (D).

As of May 2026, major forecasters rated the general election Solid/Safe Democratic. In 2024, Case defeated Patrick Largey (R) 71.8%– 28.2%.