Something’s brewing in Somerville – and it’s not a gastropub.

For the first time in a decade, 14-year incumbent Somerville mayor Joe Curtatone faces a challenger, Teamsters driver Payton Corbett, in the city’s November municipal elections.

Meanwhile, more than half of the city’s wards contested, including, for the first time in recent memory, energetic races against three incumbent members of the city’s Board of Alderman, Somerville’s equivalent of a city council.

In a city that might seem unified in its progressive bent, cracks are starting to show.

Adding to the complexity of it all: a direct line between this year’s contested races and the Bernie Sanders movement which, in Somerville anyway, won the day in last year’s Democratic primary. Sanders was in town, Monday to support the Somerville candidates, as well as those running in other municipalities.

The key issues are easy to spot: development, displacement, and affordability.  

And the tumult playing out in Somerville this year is just one manifestation of political unrest across Greater Boston over issues that tend to overlap.

Boston City Councilor Tito Jackson, challenging Marty Walsh for the mayor's seat, has made residential displacement the core of his campaign.  

In Cambridge, City Council candidates have faced increasing criticism for accepting donations from private developers (as in Somerville, some candidates have vowed not to accept such contributions). 

The campaign of Somerville mayoral would-be Corbett is, to be sure, a long shot.

“Mayor Joe” Curtatone is popular and has had ample opportunity, especially since Trump’s election, to demonstrate his progressive bona fides in a city that, by and large, prides itself on its liberal values.

But the challenge to Curtatone’s leadership is bigger than Corbett’s run for mayor, and the contested races for the city’s Board of Aldermen are proof.  

Among those races are the insurgent campaigns of local fitness gym owner and neighborhood activist J.T. Scott and biologist and former Bernie Sanders activist Ben Ewen-Campen for the city’s 2nd and 3rd wards respectively, both in and around Union Square.

Both Scott and Ewen-Campen have focused their campaigns not so much against their incumbent opponents as on how Curtatone has managed development in the city, especially in a few high-profile cases.

Among the most prominent: a recent deal involving Federal Realty Trust Investments (known locally as “FRIT”), the developer behind the transformation of Somerville’s Assembly Row.  

Earlier this year, FRIT petitioned for an exemption from a new requirement, passed unanimously by the city’s Board of Alderman, that 20% of units in big new developments be “affordable.”

Protests erupted, from residents as well as many city Aldermen, who argued the developer shouldn’t get a break; but the power to grant or deny the waiver lay with city’s Planning Board, appointed by the mayor.

Eventually Curtatone struck a controversial deal allowing for just 6% affordable housing on-site but also a $10 million donation to a city affordable housing program.

Ewen-Campen, running for Ward 3 encompassing Union Square and Prospect Hill, says attending public meetings to protest the exemption drove him to run for office.

“At one of those meetings, it clicked,” he recalls. “This was going to be about three dozen units.” -- not required to be ‘affordable’ on site – “It really made the issue concrete. “

“I think we need a board that’s willing to stand up to make sure that these appointees represent the will of the people,” he says.

J.T. Scott, running an insurgent campaign for Ward 2, which encompasses Union and Inman Squares,: agrees: The FRIT deal “was negotiated behind closed doors,” he told WGBH News. “I think that’s emblematic of the most problematic issues we have around both transparency and accountability.”

But muddling these critiques is this: These candidates aren’t running against Curtatone; they’re running against incumbent Aldermen who, in many cases, agree.

For example: Alderman Maryanne Heuston, the fifteen-year incumbent Scott is trying to unseat, and who says she did, in fact, buck the mayor on this very issue.

“I was publicly non-supportive – I testified before the Planning Board and said, ‘You cannot let them get away with his,’” she recounts. “There’s a reason people want to develop here. We’ve got something they want desperately. ”

Heuston, a senior director for the Cambridge Health Alliance, has been an Alderman for fifteen years  and, like her challenger, has avoided a negative campaign. But if challengers like Scott are running on a message of “change,” Heuston emphasizes another quality: experience.

Facing a slightly different kind of challenge is Ward 1 Alderman Matt McLaughlin, whose opponent, Elio LoRusso, a local manufacturer who, unlike other insurgent candidates, is noticeably supportive of Curtatone and, also unlike other insurgents, is supported by at least some of Curtatone’s political allies.

LoRusso, like his opponent, talks about the affordability issue but in a recent interview with WGBH News had praise for the mayor:

“Since he’s been mayor, the city’s grown,” LoRusso said. “It’s clean and it’s a city that everyone wants to come to.”

McLaughlin, another former Bernie Sanders activist, has probably been the most consistently critical voice of Curtatone among the city’s Alderman.

He too is highly critical of the FRIT deal: “This is indicative of a city where they do anything the mayor wants,” he said.

McLaughlin believes that the mayor is behind the challenge to his seat.

While there are no formal “tickets” among the candidates running for office, the group Our Revolution Somerville, which grew out of the local effort to support Bernie Sanders’ primary bid, has endorsed a slate of candidates -- including: Scott, Ewen-Campen, and incumbent t McLaughlin – who happen to be critical of Curtatone’s leadership.

(The group has also endorsed newcomer Will Mbah for one of the city’s At-Large seats; and Jesse Clingan, who is running against Omar Boukili for an open seat in the city’s 4th Ward).

Mayoral candidate Corbett was also endorsed by the group, but the endorsement was withdrawn after a report by the Boston Globe describing Corbett using insensitive language in social media posts to describe women, Asians or Asian-Americans and African-Americans.

Payton says he is sorry but also that the posts were from years ago and taken out of context.

There’s little question that the Bernie crowd has added energy to the races by its endorsements and those endorsements have pushed to the front the issue of money from for-profit developers in local races.

Insurgents Corbett, Scott, Ewen-Campen, Clingan, Mbah -- as well as incumbent McLaughlin -- have all pledged not to take contributions from developers. Their opponents have not.

Many Somerville politicos argue that the issue is overblown, if not irrelevant. But not all agree.

“To me, it’s a no brainer – I just don’t think any elected official should be taking money from these folks,” says Somerville Alderman Mark Niedergang, who is running uncontested to continue representing the city’s Spring Hill and Winter Hill neighborhoods.   

Neidergang has put his support behind incumbent McLaughlin and Clingan, but also supports Curtatone for mayor – though he is critical of the mayor’s taking donations from developers too.  

“They come before the city with development proposals that are intended to make money for themselves,” he says. “If elected officials are taking money from them, it certainly, you know, looks to a reasonable person like they could be influenced.”

An earlier version of this story misstated two names in the piece and has since been updated.