Elections
On December 27, 2012, Markey was the first to announce his candidacy to run in a special election to fill Kerry's seat after President Barack Obama nominated him for U.S. Secretary of State. Several politicians, including Kerry, endorsed Markey even before the Senate confirmed Kerry. On April 30, 2013, Markey won the Democratic nomination by defeating fellow Congressman Stephen Lynch in the primary election. He defeated Republican nominee Gabriel E. Gomez in the general special election on June 25 and completed the remaining 17 months of Kerry's term.
Markey is the longest-tenured House member ever elected to the Senate, with his 36-plus years of service exceeding that of Frederick H. Gillett, who served in the House for 32 years before moving to the upper chamber in 1925. He is the 11th oldest candidate to win a U.S. Senate special election out of more than 170 people since the passage of the 17th Amendment of the U.S. Constitution.
Markey sought a full six-year term in 2014. He defeated Republican Hopkinton selectman Brian Herr with 62% of the vote.
In the 2020 Democratic Party presidential primaries, Markey endorsed fellow Massachusetts Senator Elizabeth Warren. After Warren withdrew in early 2020, he endorsed Joe Biden.
Several Massachusetts Democrats announced primary challenges to Markey in the September 1, 2020 election, but all but 4th district Representative Joe Kennedy III dropped out, leaving Kennedy as the sole challenger. On September 13, 2019, Representative Alexandria Ocasio-Cortez, with whom Markey has collaborated on the proposed Green New Deal, endorsed Markey.
Markey defeated Kennedy with 55.6% of the vote, with overwhelming margins in Boston and the surrounding suburbs, including Kennedy's Newton, and in the college towns of Western Massachusetts. The primary race was seen by many as a showdown between the Democratic establishment, represented by Kennedy, and its new and growing progressive wing, embodied by Markey. Despite the Democratic Congressional Campaign Committee's longstanding opposition to Democratic primary challengers, House Speaker Nancy Pelosi endorsed Kennedy, whose fundraising and campaigning efforts she credited for returning the House to Democratic control in the 2018 midterm elections. Meanwhile, Markey had the support of Senate Minority Leader Chuck Schumer, Senator Elizabeth Warren, Ocasio-Cortez, and the youth-led Sunrise Movement founded in 2017 to promote the Green New Deal as a solution to the climate crisis.
Markey defeated Republican Kevin O'Connor in the general election.
In October 2024, Markey said he intended to run for another Senate term in 2026: "I'm ready to stand for reelection and that is my full intention". From the onset of his campaign, his age was a central issue. A 2024 University of Massachusetts Amherst/WCVB poll found that 72% of Massachusetts residents supported age limits for US senators. Markey, who would be 80 years old on Election Day, fended off these concerns, saying, "I'm ready for the fight [...] I am more energized [than ever]".
In October 2025, US Representative Seth Moulton announced his candidacy for the Democratic nomination for US Senate in Massachusetts, running against Markey. Moulton, who is 33 years younger than Markey, made generational change a central issue of his campaign. Markey made his progressive policies a focus of his campaign, highlighting his support of Medicare for All and pushing back against President Donald Trump.
During the primary campaign, Markey was endorsed by a slate of progressive politicians, including Senators Elizabeth Warren and Bernie Sanders and Representatives Ayanna Pressley and Alexandria Ocasio-Cortez.
On September 1, 2026, Markey defeated Moulton in the primary with approximately 65% of the vote.