Massachusetts voters are heading to the polls Tuesday to decide the Democratic nomination for U.S. Senate, with incumbent progressive Sen. Ed Markey facing a challenge from Rep. Seth Moulton, a 47-year-old Marine Corps veteran and member of the moderate New Democrat Coalition. The race is seen as a test of whether a generational argument can unseat a longtime incumbent in one of the country's most liberal states.

Markey, 80, has served in Washington since 1976, first in the House of Representatives and as a senator since 2013. He has garnered support from progressive figures such as Rep. Alexandria Ocasio-Cortez and Sens. Bernie Sanders and Elizabeth Warren. Moulton, who gained prominence for his unsuccessful attempt to block Nancy Pelosi from becoming Speaker of the House in 2018, has centered his campaign on a generational divide, arguing that new leadership is needed.

"He likes to roll the dice," Raymond La Raja, a political science professor at the University of Massachusetts Amherst, said of Moulton's approach to challenging an incumbent. "And here's another instance of him rolling a dice against an incumbent in this Senate race."

While Markey and Moulton share common ground on some issues, including abolishing U.S. Immigration and Customs Enforcement (ICE), Moulton has emphasized that the generation that grew up with the internet and will face the consequences of artificial intelligence should lead the way forward. He highlighted this during a debate, stating, "We need the generation that grew up with the internet and is going to have to live for decades with the consequences of AI to chart the way forward."

Markey countered by asserting his leadership on internet and AI safeguards, pointing to his introduction of the Youth AI Privacy Act in March. "I just want to say it doesn't make any difference whether it's called 'Siri' or it's called 'Claude,'" Markey said during the debate, stressing the need for broad protections. Moulton questioned Markey's grasp of technology, asking, "How are we going to effectively regulate and keep big tech accountable if you can't even tell the difference between big tech programs?" Rachael Cobb, an associate professor of political science at Suffolk University, noted that while Moulton is attempting to make technology a campaign focus, his base consists of more moderate Democrats. She added that "those kinds of things that happen in debates do not change the outcome of an election generally, especially when the polling is so wide between the two of them."

Polling released last week by the University of New Hampshire indicated Markey held a significant lead, with 63% of likely Democratic supporters backing him compared to 28% for Moulton.

This is not the first time Markey has faced a younger primary challenger. Six years ago, he defeated Rep. Joe Kennedy III. The dynamic of younger progressives challenging older moderates has been a trend in primaries across the U.S. for years, exemplified by Ocasio-Cortez's victory over Rep. Joe Crowley in 2018.

Several other races are also on the Massachusetts ballot Tuesday. In the 8th Congressional District, Rep. Stephen Lynch faces a progressive challenger, Patrick Roath. Six candidates are vying for the Democratic nomination in the 6th Congressional District, which Moulton will vacate. In western Massachusetts' 1st Congressional District, Rep. Richard Neal is running against teacher Jeromie Whalen. The state's Republican gubernatorial primary features a contest between veterans Mike Minogue and Brian Shortsleeve, who will compete for the chance to challenge Democratic Gov. Maura Healey, who is running unopposed for her party's nomination.

Early voting concluded Friday, and polling places are open until 8 p.m. on Tuesday.