Thirty-eight-year-old Massachusetts Rep. Joe Kennedy is set to announce Saturday that he will try to unseat 73-year-old Sen. Ed Markey in next year's Democratic primary. It's a high-stakes race that's sure to have some cascading effects in Massachusetts politics. UMass Boston political science professor Erin O'Brien discussed the race with WGBH Radio's Mark Herz. This transcript has been edited for clarity.

Mark Herz: What is Kennedy's best case for his candidacy?

Erin O'Brien: I don't have that answer for you. Honestly, I think that's the problem with the candidacy. The lane he's trying to work in is generational change, and that's just harder to do when you're a Kennedy, when you have a very similar — though less expansive — legislative record as Ed Markey.

Herz: Well what about this early polling that shows Kennedy with a sizable advantage? What do you make of that advantage?

O'Brien: Sure, he's ahead in very, very early polling, so why not throw your hat in the ring? But for Joe Kennedy to run, it's based on ambition. And there's nothing wrong with ambition, but don't try to wrap it up in things that are generational change, or a different policy position. It's just not credible coming from Joe Kennedy. And I think it's important to state that Democrats like Joe Kennedy, but they also like Ed Markey, and so I think, who wants to choose between mom and dad?

Herz: You're making it sound like perhaps it will be easy for Markey to fend him off?

O'Brien: That's not my intention. I think the polling is real. I think true die-hard Democrats, and especially, interestingly, younger Democrats, are solidly in Markey's camp. He's been really, really good on environmental policy, net neutrality, things that young people care about and care about regardless, actually, of party label. But the Kennedy name has real cachet. Joe Kennedy would not be a credible candidate against Ed Markey, given his legislative record, which isn't bad, it's just less developed, were his last name not Kennedy.

Herz: So Markey's already picked up some endorsements. He has the support of his colleague, Sen. Elizabeth Warren, and of the youngest member of Congress, Alexandria Ocasio-Cortez. How does all that factor in?

O'Brien: Endorsements matter for signaling to party elites, So yes, they matter on some level. I don't think the Elizabeth Warren one matters nearly as much as the AOC one. AOC said, "This is my partner on the Green New Deal," and the Green New Deal is something that matters very much to Democrats, and especially younger party activists. Joe Kennedy is trying to run on generational change, and the literal face of generational change in the Democratic party is AOC, and she just went with Ed Markey.

Herz: Last year we saw Ayanna Pressley unseat longtime Rep. Mike Capuano. What does it say now for another young politician leader to try to take down an established guy like Markey? What does it say about Massachusetts politics and the Democratic party?

O'Brien: It's unusual, but Seth Moulton did the same thing. I think the problem for Kennedy is Seth Moulton's primary opponent had an ethics issue. Ayanna Pressley was arguably decidedly more progressive in her district, and Massachusetts has a terrible history in terms of electing women and women of color, so she reflects demographically her district as well. Kennedy can't make either of those arguments. He's a younger white guy going against an older white guy, and his family, through no fault of his own, is decidedly establishment. So I think he's trying to ride the coattails of "The Squad," but he's not of "The Squad." It doesn't feel authentic. And I just want to emphasize, people like him. Democrats like Joe Kennedy. It's just that they've been put in an uncomfortable position having to choose between the two.