Edward Markey

US Senator Ed Markey is hitting the airwaves six weeks ahead of the Sept. 1 primary, leaning on some of the Democratic Party’s biggest progressive names to make the case that he remains one of the state’s most reliable liberal voices on Capitol Hill.

Markey’s 30-second spot features a roster of progressive politicians who’ve backed the incumbent amid his primary challenge from US Representative Seth Moulton.

US senators Bernie Sanders and Elizabeth Warren, and US Representative Ayanna Pressley each make a direct-to-camera appeal on behalf of Markey, who “is not now and never has been for sale,” Sanders says in the spot.

“When the rules aren’t working, we change them to protect the vulnerable, fight for Medicare for All, and abolish ICE,” says Pressley. “That’s Ed.”

Markey also dusts off a reference to a defining campaign ad of his from 50 years ago, when his campaign team at the time pushed a desk into an empty State House hallway and shot a commercial that thrust the then-obscure 29-year-old state lawmaker to the front of a 12-Democrat pack seeking a House seat.

“Bosses. Billionaires. Want-to-be kings. No one tells me where to stand,” Markey says to the camera in his new ad, all while striding through a brick-walled room.

The ad highlights one of the major points Markey and his supporters have sought to make as he looks to secure another term: It’s Markey, not Moulton, who is the progressive choice in the Democratic primary.

The commercial also appears designed to blunt one of Moulton’s central campaign messages that the 80-year-old Markey is too old to serve another six-year term. Rather than dwelling on policy, the spot flashes through scenes of Markey in motion, cheering before a Green New Deal backdrop, embracing supporters during a march, and addressing an anti-Trump rally.

Markey’s campaign said it’s putting $1.6 million behind the ad, which will run on broadcast, cable and digital platforms.

Moulton rolled out his first television ad late last month, highlighting the 47-year-old’s relative youth and emphasizing his calls for generational change.

How much age ultimately factors into the race remains an open question. A Suffolk University/Boston Globe poll of likely Democratic primary voters in April found that many said a candidate’s age would matter little, if at all, in deciding their vote. A June Suffolk/Globe survey found similar attitudes among general election voters: 41 percent said age was a small factor in their pick for Senate, while 33 percent said it did not matter.

Still, some Democratic voters have lamented the choices they’ve been left with this cycle between a longtime progressive incumbent and a challenger in Moulton whom some see as more moderate than they would like.

It’s not the first time Markey has faced a challenge from a younger opponent. Six years ago, he fended off a stiff challenge from then-Representative Joe Kennedy III in their Democratic primary.

This year’s contest got off to a sleepier start than the 2020 clash, but with the primary now weeks away and early voting approaching, campaigning has begun to accelerate.

Moulton and Markey faced off in their first debate earlier this month, and are currently slated to face each other in two more debates in August.

Kelly Garrity can be reached at [email protected].