Massachusetts voters will head to the polls on Tuesday for the state's primaries, with two of the top contenders for Senate continuing the ongoing theme that has been causing division within the Democratic Party—progressives vs. moderates.

Moulton, a Marine Veteran and Harvard graduate, has served as U.S. Representative for Massachusetts’s 6th District since 2015. According to his campaign website, Moulton led the creation of the 988 Suicide and Crisis Lifeline, which has connected Americans with mental health services, and has authored legislation to expand disability coverage for families affected by ALS.

Markey, who turned 80 in July, is the second-oldest sitting U.S. senator seeking reelection in 2026. He took the seat in 2013 after serving nearly 37 years in the House.

The oldest U.S. senator seeking re-election is Iowa Sen. Chuck Grassley, who has served in the Senate since 1981, making him the longest‑serving Republican senator in history.

His platform includes providing affordable healthcare, expanding educational opportunities, tackling climate change, and establishing more rights for immigrants and LGBTQ+ Americans.

His tenure and his progressive voting record have landed the Democratic incumbent several key backers, including Sens. Elizabeth Warren and Bernie Sanders, as well as Rep. Alexandria Ocasio-Cortez.

Moulton was endorsed by The Boston Globe. He also has the support of several of his current and former Democratic House colleagues, including New Jersey Gov. Mikie Sherrill.

A final Emerson College Polling survey released Sunday found Markey leading Moulton 60% to 33% among likely Democratic primary voters, with 7% undecided. The poll marked a significant improvement for the incumbent since May, when he led by just five points.

Moulton has centered his campaign on Markey's age and the need for generational change in leadership, arguing that Markey’s time as a senator has not been nearly productive enough to confront the Trump administration and advance priorities such as the Green New Deal, the latter of which has been a focal point in the incumbent's campaign.

The race has featured heavy spending, with Markey raising and spending more than $8 million compared to over $6 million for Moulton.

On the Republican side, John Deaton is the presumptive nominee for Senate.

Deaton’s platform includes reducing unnecessary spending in Washington, D.C., improving affordable housing, finding sustainable energy solutions, and strengthening the school system.

Vying to replace Moulton’s seat in the House of Representatives are six candidates: Beth Andres-Beck, John Beccia, Dan Koh, Mariah Lancaster, Tram Nguyen, and Jamie Zahlaway Belsito.

On Sunday, Lancaster withdrew from the race, endorsing Nguyen, writing, “Throughout this race, I have had the pleasure of getting to know Tram as a colleague. With every debate, every community event, every speech, I was increasingly impressed with her work ethic, backbone, and integrity. She is a union member who understands that labor rights are the backbone of our democracy and the key to the future of the Democratic Party.”

Koh, who previously served in the Biden White House, has received endorsements from former President Joe Biden and former Vice President Kamala Harris and is leading the field in fundraising, with about $4.7 million in contributions.

Polls close at 8 p.m. Tuesday. Early voting concluded last Friday.