Tuesday’s Democratic primaries in Massachusetts are likely to determine who will represent the state in Washington next year.
The state is so Democratic that its primaries are usually more consequential than general elections in congressional races. The state’s last Republican House members left office after the 1996 elections. Scott Brown, who won a special election in 2010 after the death of Edward Kennedy, was the only Massachusetts Republican to serve in the Senate since 1979.
Massachusetts Democrats will decide once again whether Senator Ed Markey is too old for another six years. They will also render judgment on Representative Stephen F. Lynch, a moderate who is the last remaining House Democrat who voted against the Affordable Care Act.
And a slice of Massachusetts Democrats north of Boston will decide whether they prefer a House candidate backed by former President Joseph R. Biden Jr. and several members of his administration, or a progressive state legislator.
Here are four big things to watch as Massachusetts votes in Tuesday’s primary.
Will Massachusetts Democrats decide Markey’s age is just a number?
Six years ago, Mr. Markey fended off a primary challenge from a much younger congressman who argued it was time for generational change.
Now at age 80, he is on the verge of doing it again.
This time, Mr. Markey, the two-term senator who began his congressional career in 1976, is seeking to defy partywide angst about old candidates that has not subsided in the two years since Mr. Biden dropped his 2024 re-election bid.
His challenger is Representative Seth Moulton, 47, who has tried to make the Senate contest about generational change. Mr. Moulton has had some success, particularly when Mr. Markey struggled during a debate to answer a question about what artificial intelligence platforms he uses.
But Mr. Markey has otherwise has not suffered public senior moments like Mr. Biden during his fateful debate or Representative John Larson of Connecticut, who froze mid-speech on the House floor. Mr. Larson went on to lose his primary last month to a challenger three decades his junior.
Recent polls have shown Mr. Markey with a comfortable lead.
Working in his favor: Just like when he beat Joe Kennedy III six years ago, he has successfully defined himself as the progressive in the race. He has hammered Mr. Moulton for his critical remarks about transgender athletes competing in sports and touted his own endorsements from Senator Bernie Sanders of Vermont and Representative Alexandria Ocasio-Cortez of New York.
The winner will face John Deaton, a Republican attorney who took 40 percent of the vote against Senator Elizabeth Warren in 2024.
How does Seth Moulton fare?
For a dozen years Mr. Moulton has been a young man in a hurry in Democratic politics.
In 2014 he ousted Representative John Tierney in a primary. Four years later he tried to topple Representative Nancy Pelosi of California just as she was about to become House speaker.
When that failed, he ran for president in 2020. Mr. Moulton never qualified for a televised debate and dropped out after just four months.
If his bid to unseat Mr. Markey falls short, what next?
Mr. Moulton, who served in the Marine Corps, has been active in recruiting and training Democratic candidates with national service backgrounds. His organization, Serve America, counts 23 members of Congress and 13 Democratic nominees for House seats this year.
“I’ve flipped 24 seats over the years from red to blue with my organization,” Mr. Moulton said in an interview last week. “There’s one person here trying to build majorities across the country in nearly everything I do.”
Will a moderate Democrat hang on?
Mr. Lynch has been in Congress for 25 years — just about half as long as Mr. Markey has served. The two faced each other in a 2013 special election primary for the Senate seat Mr. Markey now holds.
But while Mr. Markey is a dyed-in-the-wool progressive, Mr. Lynch, 71, is a moderate. He is the last sitting House Democrat who voted against the Affordable Care Act in 2010. He has referred to himself as “pro-life” in a party that has shifted strongly in favor of abortion rights. And during President Trump’s second term he voted to fund some of his administration’s immigration enforcement efforts.
Mr. Lynch did all of this while representing a South Boston-based district that is deeply Democratic. Vice President Kamala Harris won 62 percent of the vote there and Mr. Lynch has never received less than 65 percent of the general election vote.
Mr. Lynch is facing a challenge from Patrick Roath, a Boston attorney who worked as an aide to former Gov. Deval Patrick.
Like Mr. Moulton, Mr. Roath, 39, is running on a campaign of generational change. But unlike Mr. Moulton, he is campaigning from the left, aiming to cleave progressive voters from Mr. Lynch by criticizing his positions on health care and immigration.
Who will replace Moulton in the House?
There is only one Democrat running for Congress this year whose campaign has touted video testimonials from both Mr. Biden and Ms. Harris: Dan Koh, a former Biden White House aide who is in a five-way primary to replace Mr. Moulton.
Along with the former president and vice president, Mr. Koh touts endorsements from five former Biden administration cabinet secretaries, but in a moment when Democrats have shown themselves not very nostalgic about the Biden era it is unclear how many voters are swayed by the likes of Gina Raimondo, a former commerce secretary and former Rhode Island governor. (More likely to move votes: More than $700,000 from pro-AI super PACs that support Mr. Koh.)
Mr. Koh’s main competitor is Tram Nguyen, a state legislator who has sought to consolidate the district’s progressive voters. She has endorsements from Representatives Ayanna Pressley and Lori Trahan, who first won her seat in 2018 after defeating Mr. Koh in a primary by just 145 votes.
Ms. Nguyen won a late endorsement on Saturday from Mariah Lancaster, a veterinarian who until then had been a candidate in the primary.