US Sen. Edward Markey went directly after the record of his Democratic primary opponent, US Rep. Joseph Kennedy III, in a Monday night debate, attacking Kennedy’s decision to work for a Republican prosecutor on Cape Cod and the islands after law school and challenging his progressive credentials.

Kennedy returned fire, reminding voters that Markey opposed busing to desegregate Boston Public Schools when he first came to office, and voted for a 1994 crime bill that has been criticized on the left for disproportionately harming minority communities.

The exchanges, which started right from the start of the hour-long debate, appeared to signal a change in strategy from Markey, who in prior debates has largely avoided direct criticism of Kennedy and focused more on his own record.

In addition to citing Kennedy’s work for the Republican prosecutor, Markey also knocked him for taking two years to sign on to Medicare for All and for not discussing climate change when he delivered the Democratic response to the State of the Union in 2018.

“Congressman Kennedy is a progressive in name only,” Markey said.

The debate was the third of the campaign and the second in a week hosted by WPRI 12 in Providence, Gannett’s southeastern Massachusetts newspapers, and UMass Dartmouth. The debate also aired on sister stations in Springfield and Albany, whose viewership includes Berkshire County.

The first question of the debate was for Markey, and focused on his support for the 1994 crime bill, which included strict new mandatory minimum sentences for minor drug offenses and other crimes.

Markey said that every member of the Massachusetts delegation voted for that bill at the time, and he said that in addition to sentencing guidelines that he now considers to be “totally wrong,” it also contained a ban on assault weapons.

The incumbent then pivoted to Kennedy and his decision to take a job out of Harvard Law School with Cape and Islands District Attorney Michael O’Keefe, who Markey called “the most conservative Republican right-wing district attorney in a generation” in Massachusetts.

“He could have worked for anyone. He could have worked for the Innocence Project. He could have worked as a tenants rights attorney, but instead he decided to go and work for a right wing Republican who opposes the kinds of progressive changes we’re looking for.”

Kennedy said that instead of criticizing him, Markey should be celebrating young progressive prosecutors going to work in more conservative district attorneys’ offices as “the change we want to see.” After the debate, he said he interned with O’Keefe’s office while in law school, and was offered a job after school where he worked with Democrats and Republicans on staff on “entry-level” assault, operating under the influence, and domestic violence cases.

“He was a Republican district attorney who hired a guy named Kennedy to go in as an entry level prosecutor. We of course had disagreements,” Kennedy said.

He then questioned why after a 47-year career in public office Markey has not been able to get more accomplished to reform the criminal justice system and address the inequalities facing communities of color.

“You might be known for some things in your time in office, senator. Racial justice and criminal justice is not one of them,” Kennedy said.

Those opening moments of debate set the tone for the rest of the night as the two Democrats sniped at each from six-feet apart over who had the strongest claim to the progressive mantle and whose record of leadership best suited them to represent the state in the Senate.

Markey, as he has throughout the campaign, ticked off bills he has filed that became laws. He highlighted his sponsorship of the Green New Deal, a resolution he filed with Rep. Alexandria Ocasio Cortez of New York that has not passed, and his work on net neutrality and an Alzheimer’s research law.

“We’re still waiting for a major piece of legislation to be passed by the congressman that merits his promotion to the United States Senate,” Markey said.

At one point when asked why the Baby Boomer generation should continue to have such influence over institutions like Congress, Markey, 73, said, “It’s the age of your ideas that are important.”

Kennedy, for his part, said leadership in the Senate should be about more than just the bills someone files and the votes they take, but also their ability to build coalitions to bring about change.

The congressman touted the work he did in 2018 to campaign and fundraise for Democrats around the country, which led to Democrats taking control of the House and having the power to impeach President Trump and hold the administration accountable.

“When you compare my record about going out and trying to actually create the change that is necessary, I was in all those states, and Senator Markey was in zero,” Kennedy said.

Kennedy also challenged Markey’s refusal to sign the same kind of pledge he did during his 2013 campaign for Senate to limit outside spending their race. Markey has said that progressive groups like Planned Parenthood and Environmental Massachusetts, which recently announced plans to spend $200,000 for Markey through its action fund Environment America, should be allowed to have a voice.

Kennedy, however, accused Markey of reversing his position, and pointed out that he has asked a super PAC being set up by his supporters to stop and donate whatever money had been raised to Black Lives Matter.

The debate wasn’t all divisive, though.

In the wake of the killing of George Floyd, both Democrats said they supported the idea of “rebalancing” budgets to take money away from police departments and put it into education and social services.

They also agreed that the Electoral College should be abolished, that there should not be term limits on Congress, that undocumented immigrants should be granted temporary unemployment benefits during the COVID-19 pandemic, and that the Mashpee and Aquinnah Wampanoag tribes should be allowed to build casinos on tribal land in Taunton and Martha’s Vineyard.