How many Democratic congressional candidates can you squeeze onto one stage?

It sounds like the set-up to a mildly humorous joke. But in the crowded Third District congressional race, it’s a serious question.

For the record, on Tuesday night in Hudson, the answer was: 13. A baker’s dozen of Democrats packed the stage at that town's Portuguese Club, sitting awkwardly close together and weighing in on everything from the environment to surveillance to President Trump.

The strangest part? That wasn’t even the whole field. Jeff Ballinger, a fourteenth candidate, had arrived at the forum hoping to participate, only to be told that organizers had learned of his candidacy too late for him to take part. Ballinger’s very existence seemed to take the others by surprise: before they event, they were still buzzing about another new entry, Lenny Golder of Stow.

Even if you’re obsessed with local politics, you’ve probably never heard of Golder or Ballinger. But other candidates in the MA3 race should be more familiar. There’s a state senator (Barbara L’Italien); a former top aide to Boston Mayor Marty Walsh (Dan Koh); a former nominee for Lieutenant Governor (Steve Kerrigan); and a former US ambassador turned reality-TV star (Rufus Gifford).

Video: Meet The Candidates For the Mass. Third District

What’s more, the MA3 race is packed with potential firsts. If elected, Beej Das would be the state’s first Indian-American congressman. For her part, State Representative Juana Matias would be the first Latina to join the Mass. delegation.

If Bopha Malone wins, she’d be Congress’ first-ever Cambodian-American, and Alexandra Chandler would be the first transgender US representative.

It’s a diverse field for a very diverse district. The Mass. Third stretches from the New Hampshire border to the middle of the state, and includes urban Democratic strongholds like Lowell, conservative enclaves like Dracut, and leafy liberal bastions like Concord.

Which raises an obvious question: is there any particular sensibility that ties the Third together?

Chris Lisinski, who’s covering the race for the Lowell Sun, says there might be.

“There seems to be some sentiment among people in the district that they’re proud of their district, and outsiders kind of get a bad look here,” Linsinski says.

That could be bad news for Dan Koh, Walsh’s former chief of staff, who moved back into the Third after Congresswoman Nikki Tsongas announced she would retire. Then again, Koh was raised in an Andover neighborhood that’s part of the Third — and he’s already raised $1.6 million, more than any competitor.

Whoever wins the primary won’t have a free ride in the general election. Republican Rick Green, the CEO of 1A Auto, is waiting in the wings. Still, the eventual Democratic victor will have the confidence that comes from beating thirteen opponents — and maybe, at this rate, one or two more.