Sen. Ed Markey and Rep. Seth Moulton squared off again Monday in a live televised Democratic primary debate.

The two faced off ahead of the September 1 Massachusetts U.S. Senate primary election. Markey, the incumbent, has served in the Senate since July 2013 and is seeking a third full term. Moulton has represented Massachusetts’ 6th Congressional District since 2015 and is vacating his House seat at the end of the year.

The candidates met for a one-hour debate Monday in Dedham. The debate was moderated by Boston 25 News anchor Kerry Kavanaugh and GBH politics reporter Adam Reilly. 

The two fielded questions on affordability, health care and Iran, among other issues. Both candidates used questions to highlight their own records while attacking their opponent.

“Senator Markey, I have seen Americans lose their lives because of your vote to send us to war in Iraq,” Moulton said. “Do not question my commitment to peace in the Middle East.”

Markey later said he regretted his 2002 vote.The following year, he voted against then-President George W. Bush’s $87 billion funding request for the war.

Both candidates have said they oppose the war, with Markey calling it a “moral tragedy and economic disaster.” 

For his part, Markey said he would step down if he could no longer effectively serve the state due to his age. He also turned the question back on Moulton.

“I would step down,” Markey said. “But Congressman Moulton should step down. Any public official should step down if they cannot serve. That is a responsibility.”

Moulton, who is 47, again called for Markey, who is 80, to release his health records.

This was the candidates’ second debate. They previously met last month, fielding questions on their experience, health care and transgender rights. 

During Monday’s debate, Markey did bring up the transgender rights issue again. He said that Moulton “has thrown those (trangender) kids under the political bus.”

During Monday’s debate, Moulton apologized to transgender children and the broader transgender community. Moulton has faced backlash following the 2024 election when he told the New York Times in an interview that he would not want his daughters “getting run over on a playing field by a male or formerly male athlete.”

“To the trans community feeling the weight and the pain of the Trump administration policies, I deeply recognize your trauma, and I’m sorry if my comments hurt you,” Moulton said Monday. “If you’re in the trans community or you’re a trans kid feeling the weight of the Trump administration and the Supreme Court, you matter, you’re valued, and I will always have your back.”

Throughout the July debate, Markey highlighted his legislative accomplishments and ongoing priorities in Washington. Moulton countered by arguing that the Democratic Party needs new leadership and broader electoral success to regain control of Congress and enact meaningful change.

There will be another debate between the two candidates on August 20.

Massachusetts voters will cast their ballots on September 1 in the Democratic primary. The winner will face presumed Republican nominee John Deaton in the November general election. 

A new University of New Hampshire poll that came out last week suggests that Markey’s lead over Moulton is narrowing. Among likely Democratic primary voters, 41% said they support Markey, while 35% back Moulton. An additional 24% are still undecided, and 1% would vote for another candidate.

Markey’s support has fallen from 46% in April. Undecided voters have increased in the last two months as well, rising from 15%.

Polling from May similarly found Markey holding a five-point lead over Moulton. The Emerson College Polling found Markey leading 37% to 32%, with 29% of voters undecided.

An April 15 poll by the Suffolk University Political Research Center and the Boston Globe showed 79-year-old incumbent Markey at 47%, while 47-year-old Iraq War veteran Moulton had edged up to 30.4%.