Representative Stephen Lynch of Massachusetts, a centrist Democrat, won his primary on Tuesday, according to The Associated Press, defeating a younger challenger who ran to his left.

Mr. Lynch, a 71-year-old former ironworker, faced Patrick Roath, a 39-year-old lawyer who worked as an aide to former Gov. Deval Patrick of Massachusetts. The contest reflected the generational and ideological divisions running through the Democratic Party in this year’s primaries.

Mr. Lynch’s victory puts him in a strong position to win another term representing Massachusetts’s Eighth Congressional District, a heavily blue area covering parts of Boston — including the historic Beacon Hill neighborhood and South Boston — as well as parts of the South Shore suburbs.

During the campaign, Mr. Roath attacked Mr. Lynch for being the last remaining Democrat in Congress who voted against the Affordable Care Act and for supporting the Laken Riley Act, a measure signed by President Trump that requires the detention of migrants who enter the country without authorization and who are arrested or charged with certain crimes.

As he had in previous primaries, Mr. Lynch leaned on his experience in Congress and his support from unions to argue he could best represent the district. He also cited his position as the ranking Democrat on a subcommittee on artificial intelligence and his seat on the House Committee on Oversight and Accountability.

“We need more people in the middle to give that strength to the Democrats so that we can actually be a party that governs, and not simply a party of protesters,” Mr. Lynch said on GBH’s “Boston Public Radio” in August.

One advertisement featured black-and-white photos of Mr. Lynch against the Boston skyline, clipped into a harness on the job as an ironworker.

Aligned with the progressive wing, Mr. Roath called for abolishing Immigration and Customs Enforcement and for enacting a “Medicare for all” health care system.

“Congressman Lynch has been in office for 25 years now,” Mr. Roath said in one advertisement. “He’s not a bad guy, but he’s not the leader we need right now.”

Leaders We Deserve, a group that supports young congressional candidates and is led by David Hogg, a gun control activist, spent more than $450,000 on mailers attacking Mr. Lynch and boosting Mr. Roath. But Mr. Lynch outspent his opponent by roughly $300,000, according to the latest filings, drawing on funds he raised before this cycle.

Another member of Massachusetts’ congressional delegation, Senator Ed Markey, also dispatched a younger challenger — Representative Seth Moulton — in the Democratic primary on Tuesday night. But Mr. Markey is a progressive, while Mr. Lynch is not.

In November Mr. Lynch will face the Republican nominee, Robert Burke, a retiree who ran unsuccessfully in 2022 and 2024.