US Rep. Joseph Kennedy III’s possible challenge of US Sen. Ed Markey was on display Monday at an annual Labor Day breakfast in Boston as more than 200 electrical workers with Kennedy signs filled the sidewalks of the Park Plaza in advance of the event.

IBEW business manager Lou Antonellis said the Dorchester-based union is supporting Kennedy– even before he has announced his candidacy– because the status quo isn’t good enough. “And it’s not about Ed Markey,” he added. “It’s about Joe Kennedy and what he stands for. He’s a younger, stronger voice. Being Labor Day, there’s not a better advocate for labor. You know, a stronger voice. That’s what Joe Kennedy provides.”

The 38-year-old Kennedy lives in Newton, and after six years in Congress, he’s mulling a bid for the Senate. He said he is humbled by the people who came out to urge him to run, but he’s got business to take care of before deciding whether to challenge his fellow Democrat.

“I’ve got some things we’re still working through, obviously family and then getting around the state and talking to voters,” he said. “This ultimately is not a question of anybody running against anyone else. You run for the seat. And in order to do so you need to make sure you get the support of people across the state.”

Markey, who is 73, was at the breakfast on Monday, and he had his supporters with him. Speaking to reporters, he said nothing about his potential opponent, but he repeated that he’s planning to run on the basis of his record.

“I’m running straight out for the next year for reelection,” he said, “and I’m going to run on the issues that people want me to fight for and I have been fighting for on the Senate floor throughout my entire career: women, workers, climate change, gun safety protections, and I’m gonna continue to do that.”

To some, a Kennedy run for Senate could resemble former Boston City Councillor Ayanna Pressley’s challenge of Congressman Michael Capuano. Pressley’s candidacy was viewed as a rebuttal of the old Massachusetts politics – when newcomers waited their turn rather than challenge an incumbent.

Boston Mayor Marty Walsh says a Kennedy run could be another shakeup in politics here. “I’ve already told Sen. Ed Markey that I’m supporting him, and I’ve talked to Joe Kennedy since then, and we’re gonna talk again,” the mayor said. “But I think last year, when Ayanna Pressley took on Mike Capuano, it was kind of the first time we saw that type of disruption, and that’s a new brand of politics that we’re seeing here in Massachusetts.”

That brand of politics was also embodied in last year’s election of Boston state Rep. Nika Elugardo, who won her seat after beating a high-ranking Democratic incumbent. But in a Kennedy-Markey match-up, she said she’d go with the one who’s already in the Senate. Elugardo says Markey has been a mentor to her, and over the years she’s watched him take many people under his wing.

“I’ve watched him do it with everyone from servers who are serving food in rooms where we are, when the other politicians are hanging out with the bigwigs, and he’s like deeply invested in finding out who this person is and building them up and encouraging them. That’s the kind of politician that we need, so I will have his back until he’s done,” she said.

Should Kennedy challenge Markey, one dynamic in the race would be who’s viewed as the more progressive candidate on things like climate change. Markey is a leading voice promoting the so-called Green New Deal.

But if it comes down to name recognition, even an incumbent senator faces a challenge against a representative of the Kennedy dynasty.

Organized labor could also prove key — and labor activists are already starting to dig trenches on either side, in advance of a race that hasn’t yet started.

This story was published by WBUR 90.9FM on Sept. 3. The Reporter and WBUR have a media partnership in which the two news organizations share content.