Seth Moulton

Incumbent Sen. Ed Markey and challenger Rep. Seth Moulton are set to meet in a second primary debate in the Massachusetts Senate race on Monday night.

The candidates will take the stage at 7 p.m. Monday in a live debate hosted by Boston 25 and GBH news.

The debate comes just under a month out from the Sept. 1 Democratic Primary Election, in which voters will select the Democrat to face Republican candidate John Deaton in the November election.

Monday’s debate follows the first July 8 face-off between Moulton and Markey on WWLP-TV in Western Massachusetts, during which candidates covered topic including Donald Trump, Markey’s octogenarian age, Moulton’s comments on trans athletes, and more.

Markey’s team in a message to supporters Sunday called the second debate a “crucial opportunity for our campaign to share the vision, values, and legislative agenda that make Ed a progressive champion.” Supporters of the incumbent are set to gather in Dedham for a watch party.

Markey’s team did not respond to a request for comment on the upcoming debate as of Sunday evening.

The incumbent senator has served in Congress since 1976 and held his U.S. Senate seat in Massachusetts since 2013.

Moulton spokesperson Taylor Hebble said Moulton is looking forward to holding Markey “accountable for his previous false statements.”

“As a Herald investigation uncovered, Markey has taken corporate PAC money during this campaign – despite repeatedly lying about it in past debates, on social media, in fundraising emails, and in the media,” Hebble said. “Markey has also taken tens of thousands of dollars from fossil-fuel lobbyists – and tried to hide it by returning the money during his last re-election and then re-accepting it after he won. Markey owes it to voters to provide answers about these lies during the debate.”

Moulton “believes it’s time for new leadership and bold ideas to help families in Massachusetts struggling with the high cost of housing and energy,” Hebble added.

Moulton announced an endorsement from Pennsylvania Rep. Chrissy Houlahan on Sunday, noting she “pulled off a historic red-to-blue flip in a district held by Republicans for 160 years” and “knows what it takes to win tough fights” in a social media post. The announcement follows local State Sen. Nick Collins endorsement of Markey on Saturday.