The cause was colon cancer, said his father, Michael O. Gayle. Mr. Gayle was diagnosed with cancer in March 2016 and was successfully treated before suffering a relapse last year.

Mr. Gayle was described as making an outsize impact on the campaigns and causes he served over the eight years since he had graduated from college.

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He had his first brush with national politics in 2012, when he became a driver and assistant to Kaine, the former Virginia governor then seeking the Senate seat vacated by retiring Democrat Jim Webb. Mr. Gayle drove Kaine more than 60,000 miles around the state, according to People magazine, during the candidate’s successful run.

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“From 7 a.m. to 10 p.m. or later, I was driving him and staffing him, keeping him on schedule, briefing him on who he was meeting and keeping his morale up — whether that was by an early-morning hike or talking sports trivia,” Mr. Gayle told People in a 2016 interview. “I spent more time with him than his wife did during that stretch, and he spent more time with me than any of my friends did.”

After working briefly for the Senate Democratic Steering and Outreach Committee, he joined the Democratic Congressional Campaign Committee as a spokesman during the 2014 midterm elections. He was named a rising star by the publication Campaigns and Elections in 2015.

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Clinton, the former first lady, U.S. senator from New York and secretary of state, hired him to work as a spokesman in her Brooklyn headquarters during the campaign that she would lose to businessman and reality TV star Donald Trump. Mr. Gayle’s cancer diagnosis came during the campaign.

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“Watching him throughout the campaign was nothing short of inspiring,” Clinton told a publication of Mr. Gayle’s alma mater, Clemson University.

He was midway through his chemotherapy treatment when he wrote to Clinton to vouch for his former boss as a potential vice presidential running mate. At the time, Kaine, who hailed from the strategically important state of Virginia and whom Clinton ultimately selected, was among the likely contenders.

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“I can personally attest to his incredible character, integrity, competency and ability to get things done,” Mr. Gayle declared in an email to Clinton, according to People. “I believe he would be a great choice, and be an effective governing partner.”

Announcing Mr. Gayle’s death on Facebook, Kaine wrote that “all who crossed Tyrone’s path were affected by his warmth, humor, and positive energy.”

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Harris offered her condolences on Twitter. “Tyrone Gayle was an invaluable and beloved member of our team and family,” she wrote. “He never lost faith in our ability to do good for the people in this country.”

Tyrone Oliver Gayle was born in Toronto on Nov. 12, 1987. His father, a pediatric critical care specialist, and his mother, a nurse, are from Jamaica.

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Mr. Gayle grew up in Jacksonville, Fla., where he worked on his high school newspaper and excelled at track. In 2010, he received a bachelor’s degree in communications studies from Clemson, where he continued to run track.

Mr. Gayle’s early work in Washington included jobs at the Center for American Progress and Media Matters, both progressive organizations. Survivors include his parents, Dr. Michael O. Gayle and Ann ­Gayle, both of Jacksonville; a sister; and his wife, Beth Foster Gayle of Washington, whom he married in May. Kaine officiated at the ceremony.