Seth Moulton

We know this much about the 2026 race for U.S. Senate in Massachusetts: Voters will see the candidates face off in at least two debates before the Sept. 1 primary election.

Everything else is ... well ... open to debate.

Here’s what we know for sure: The two Democrats in the race, incumbent U.S. Sen. Ed Markey and U.S. Rep. Seth Moulton, will face each other in an Aug. 20 debate sponsored by WBUR-FM, The Boston Globe and WCVB-TV in Boston.

WCVB-TV anchor Ed Harding, joined by a journalist from each outlet, will host the televised showdown.

Then there’s the June 16 debate sponsored by WBZ-TV and anchored by veteran politics reporter Jon Keller.

In a twist that all concerned swear does not scream “political stunt,” Moulton, D-6th District, will face Republican hopeful John Deaton.

So far, Markey is a no-go.

And, as you might expect, it’s all become a bit of a thing.

“We should be leading by example and engaging in transparent and robust debate in front of the voters,” Moulton’s spokesperson, Taylor Hebble, said. “Seth is an open book.”

Markey is ”really ... ceding the floor at a time when the commonwealth wants and needs a fighter who isn’t going to shy away from a challenge," Hebble continued.

Speaking to reporters as he dropped off his nominating petitions at the Secretary of State’s Office on Monday, Deaton issued a similar challenge.

“Hopefully Ed shows up, right?” he asked, adding that Markey, 79, has been in “office since I was 6 years old.”

“You have 53 years (in office). If you can’t show up and defend your record —and that’s why he doesn’t want to show up, because he can’t defend those 53 years in a good way,” Deaton, 58, said.

Markey’s campaign did not respond to requests for comment for this column.

The debate over debates got rolling earlier this month when the state Democratic Party threw some social media shade at Republican gubernatorial candidate Mike Minogue over his challenging Gov. Maura Healey to a pair of debates before Labor Day.

Minogue, a wealthy biotech executive, walked off with the Republican endorsement at the state GOP’s convention in Worcester last month.

But he still has to win the party’s nomination in September.

Baker administration alum Brian Shortsleeve, who barely met the minimum threshold for the primary ballot, had said he’s in the race until the end.

Read More: Shortsleeve battles GOP pressure to drop out of Mass. governor’s race: ‘It’s an insiders’ game’

Moulton’s camp got in the act by amplifying the state Democratic Party’s posts on X. That prompted Deaton, who’s never met a cheeky social media post he didn’t like, to throw down the debate gauntlet.

Moulton swiftly accepted the challenge, stipulating that “we do it whether or not (Markey) agrees to join us. I’m looking forward to debating our different visions for the future of our country. The people deserve to hear from us.”

The Salem lawmaker has cast the fight with Markey as a generational one. He’s paid tribute to his decades of service, but says it’s time for a new generation to take the reins of power.

Deaton, meanwhile, has cast himself as an independent and critic of President Donald Trump who will have one test: “Is it good for Massachusetts and America?”

On Monday, Deaton rejected the suggestion that the debate was a political stunt since he was facing, in Moulton, a candidate who might not survive this fall’s Democratic primary.

But he also acknowledged that there was no way he was going to let it pass him by.

“I think that it’s an opportunity for people, including Democrats, to get a good look at me, and say ‘Let’s see who has the right ideas,’” he said. “I keep telling everybody, people are not looking for ideology. They’re looking for solutions to their problems. So I’m bringing solutions.”

Deaton comes into the race with an existing statewide profile after unsuccessfully challenging U.S. Sen. Elizabeth Warren, D-Mass., in 2024.

Deaton upped the debate ante on Thursday, challenging the eventual winner of the Democratic primary to five, single-issue debates starting after Sept. 1 and running right up until Election Day.

No topic is off the table, he said, adding “Hell, we can even have a one-hour debate on Markey & Moulton’s FAVORITE topic: all things Donald Trump.”

With a week to go before the Democrats’ nominating convention in Worcester, Moulton, 47, has steadily closed a polling gap with Markey. He trailed the Malden pol by 5 points in an Emerson College poll earlier this month.

Moulton’s camp has insisted it has the support it needs to make the fall ballot, and now feels confident about its chances in September.

“This race is about allowing voters across the commonwealth to get to know Seth better,” Hebble said. “Because what we’ve seen in all of the public polling, and what we’ve seen on the ground, is that when people know Seth and know who he is, they want to vote for him.”

Markey, meanwhile, appears to be exercising the incumbent’s prerogative of ignoring the competition — though that hasn’t always been the case.

Markey debated his lone primary challenger, former U.S. Rep. Joe Kennedy, in February 2020 — some seven months before the fall intraparty contest.

Another debate in August of that pandemic year saw Markey committing what was considered political heresy at the time by sharply criticizing the Kennedy family.

Markey also had one debate with his Republican challenger, Kevin O’Connor, in October 2020, moderated by WGBH-FM hosts Jim Braude and Margery Eagen.

Veteran Western Massachusetts political consultant Matt L. Barron says he’s all in on debates. In fact, “we could use more of them — there aren’t enough opportunities to hold officeholders and candidates accountable."

But an Aug. 20 debate, which comes just two days before the start of early voting? That “doesn’t serve the voters well,” he said.

And the WBZ-TV debate? He’ll pass.

“It seems more of a stunt than a real effort at political discourse,” Barron said.

Voters will have the final word at the primary on Sept. 1.