A member of the Democratic Party, he has served as the U.S. representative for Hawaii's 1st congressional district since 2019, which covers the urban core of Honolulu.

After high school, Case traveled for a year in Australia, where he worked as a jackaroo on a New South Wales sheep station, and in New Zealand.

In 1981, Case graduated from the University of California Hastings College of Law in San Francisco with a Juris Doctor.

From 1981 to 1982, Case served as law clerk to Hawaii Supreme Court Chief Justice William S. Richardson.

In 1999, after he led an effort to replace the State House leadership, his Democratic peers elected him Majority Leader.

"[14] On January 21, 1997, in the House Judiciary Committee, Case cast the lone vote against advancing HB117, which would allow a referendum to effectively constitutionally ban gay marriage.

[16] When he was up for reelection in November 1998, he publicly opposed the referendum because, he said, "changing the Constitution would go against its intended purpose—protecting the rights of the minority against the will of the majority.

[19] U.S. Representative Patsy Mink died on September 28, 2002, one week after the primary election, leaving her 107th Congress (2001–2003) seat vacant.

Case ran in a second special election on January 4, 2003, for Mink's 108th Congress seat, facing more than three dozen other candidates.

In 2004, Case defeated Republican challenger Mike Gabbard, a social conservative who focused almost exclusively on gay marriage issues.

[22] In the general election, Case carried Hawaii's 1st congressional district by a 50-point margin, 73.1%—23.1%,[23] defeating Republican Campbell Cavasso.

Of those bills, Congress passed H.Con.Res.218 recognizing 100 years of Filipino-American immigration to America, the Kaloko-Honokohau National Historical Park Addition Act (H.R.546 / Public Law No.

Postal Service facility in Paia, Hawaii, as the Patsy Takemoto Mink Post Office Building, and the Kilauea Point National Wildlife Refuge Expansion Act (H.R.

In June 2006, President George W. Bush achieved much of the bill's goals by issuing a public proclamation creating the Papahanaumokuakea Marine National Monument under the authority of the Antiquities Act of 1906.

[32] The caucus was also formed to encourage greater education for House members on the unique environmental, defense and economic issues of island nations and states in the Pacific Ocean.

The bill would regulate tour airplane and helicopter flights and, among other things, set decibel limits over residential neighborhoods, prohibit overflights of military facilities, national parks, and residential areas by air tours and require a sterile cockpit.

[35] In August 2021, Case joined a group of conservative Democrats, dubbed "The Unbreakable Nine", who threatened to derail the Biden administration's $3.5 trillion budget reconciliation package meant to tackle the nation's infrastructure.

Case's initial opponent was the early favorite in the race, Mayor of Honolulu Jeremy Harris, also a Democrat.

Despite high polling numbers, Harris abruptly dropped out of the race in May 2002 because of ongoing campaign spending investigations.

Lieutenant Governor Mazie Hirono dropped out of her race for mayor of Honolulu to challenge Case in the primary.

A later entrant into the Democratic primary was D. G. "Andy" Anderson, the former Republican state chair and aide to former Honolulu Mayor Frank Fasi.

Case told Hawaii voters that his campaign was one of government reform and the future, as opposed to Hirono and Anderson, who represented the "Old Boys' Network" and a status quo past.

In one of the closest primary elections for the Democratic gubernatorial nomination in Hawaii history, Hirono beat Case, 41% to 40%, with Anderson a distant third with 17%.

[8] On March 29, 2009, Case announced his candidacy for Hawaii's 1st congressional district seat, being vacated by Neil Abercrombie.

[47] It was unlikely either Democrat would drop out; they represented different views and had already faced off in a 2003 special election for Hawaii's 2nd congressional district, which Case won.

[52][53] Case initially said he would run in the next primary against Hanabusa, but later changed his mind and dropped out of the race, citing party unity and his third-place finish.

In 2001, he married Audrey Nakamura, a former classmate from Hawaii Preparatory Academy, who is a flight attendant with United Airlines.