BRUNSWICK, Maine — The fireplace crackled as Democratic Gov. Janet Mills laid out her vision for beating Susan Collins to a room of supporters in late January. Then came the questions about her primary opponent, Graham Platner.

Platner, one attendee noted, was very successful on social media. A second pointed to his support among young people and asked Mills whether she would support him if he became the party’s nominee.

“I am a Democrat,” Mills answered, before pivoting to how she sought as governor to make the state more affordable for young Mainers.

Mills’ Democratic primary opponent isn’t her favorite subject. She would rather talk about how she expanded Medicaid, bolstered protections for reproductive rights, and, most recently, challenged President Donald Trump over the surge of immigration enforcement in the state — issues that conveniently allow the governor to draw contrast with Collins, the five-term Republican who Democrats must unseat in order to take back control of the Senate.

But Platner, a political newcomer, has made himself all but unavoidable in conversations about the Maine Senate race. The 41-year-old oyster farmer and combat veteran is unlike any other recent popular candidate the state has seen: He is brash. He is progressive. He has drawn crowds of hundreds of people, national attention and millions in campaign dollars.

Platner’s meteoric rise reflects a growing frustration with the Democratic establishment and voters’ interest in a new generation of leaders. He is campaigning not just against Collins but against a “billionaire class,” running a campaign in the style of Sen. Bernie Sanders (I-Vt.), who endorsed him.

His battle with Mills comes at a moment when the stakes for Democrats could hardly be higher. Though the Maine Democratic Party doesn’t take positions in primaries, some establishment figures like Senate Minority Leader Chuck Schumer have backed the moderate governor, who they believe is their best shot at defeating Collins to win back the Senate in 2026.

The challenge for Platner is that he is running on a vision of disruptive progressivism and generational change in Maine, the oldest state in the nation and one with a long track record electing senators perceived as moderates within their parties. Mills would largely fit that image; Platner would blow it up entirely. But he is betting that voters now want what he is offering — and his early support makes it hard to ignore the possibility.

“If you look at everyone from Bill Cohen to Angus King to George Mitchell to Susan Collins and Olympia Snowe, there’s a strong, moderate streak there when it hits November,” said Adam Cote, a Maine lawyer and veteran who ran for governor in 2018, coming in second to Mills in the Democratic primary. “In the primary, I don’t know.”

While public polling in the race has been relatively scarce, an internal poll released by Platner’s campaign last month had him up by double digits over Mills. He has 283,000 followers on Instagram compared to 61,000 for Mills and 25,000 for Collins. His campaign boasts of a 15,000-person strong volunteer network. Through the end of December, he raised $7.8 million to $2.7 million for Mills, enough to begin running TV ads more than four months in advance of the June primary.

“My wife makes this joke. I’ve been just saying the same bullshit for years, ranting on about structural inequality, ranting on about, like, American history and how we need to reconnect with things. Nobody cared about me because I was a random dude in Sullivan, Maine,” Platner said in an interview. “I’m now running for United States Senate, and I get to have this conversation at a national level.”

Both in style and substance, Platner is unlike any candidate who has risen to the highest levels of Maine politics in recent decades. Even before he faced a litany of controversies in the fall — including a series of offensive old Reddit posts for which he apologized and a tattoo of a Nazi symbol that he had covered up — the Sullivan oysterman was building an operation different from any Maine Democrat.

Platner does not like the label of progressive, but where he differs with Mills on policy, his positions are largely to her left. He has backed progressive priorities like Medicare for All, described Israel’s military actions in Gaza as a genocide, and favors abolishing Immigration and Customs Enforcement.

Asked whether progressives can win in Maine, Platner pointed to polling showing Sanders’ popularity despite his finishing narrowly behind Joe Biden in the 2020 presidential primary.

Although more progressive state lawmakers have been elected from southern Maine over the past few election cycles, further-left candidates finished far behind the more moderate ones in statewide primaries for governor in 2018 and Senate in 2020.

“There’s a reason why [Rep. Chellie] Pingree never ran for governor,” said Mark Brewer, a political science professor at the University of Maine. “She recognizes it would be very difficult for someone that’s as far to the left as she is to win statewide in Maine. And when we look at the Democrats who do win statewide, they look like Janet Mills.”

Some of Platner’s appeal may come less from his specific progressive stances than from his ability to capture the energy of Democratic voters upset about the state of the country — and at their own party for not doing enough to stand up to it. Trump’s second term led even people who were not previously politically active to show up for protests, with many aligned with Platner’s style of economic populism, said Andy O’Brien, a Maine writer and activist supporting Platner.

“The Trump administration has just been so extreme that I think it’s really radicalized average, ‘normie’ voters,” O’Brien said.

In an interview, Platner recalled going to a local Democratic party meeting in early 2025 and coming away frustrated that attendees were talking about bylaws, not Trump. In his view, there was pent up grassroots energy to fight the administration — shown, for example, by large No Kings protests in the state — but few organized outlets to turn it into action.

His campaign proved one outlet for that energy. Following a surge in ICE activity in Maine in January, Platner led a protest at Collins’ offices in Portland and Bangor, calling on the senator to cut funding to the agency. Dozens of supporters showed up in single-degree temperatures.

“I’m a supporter of Graham Platner because we need a U.S. senator to represent Maine who will be honest with us, who will be truthful with us, and will work for us,” said Laura Neal, a Bar Harbor resident who attended the protest with a sign reading “My Cat Hates ICE.”

Like many Platner backers, Neal doesn’t dislike Mills, but thinks it is time to move on. “I think Governor Mills has done a great job, and it’s time for new energy,” she said.

In much of the national conversation about the Maine Senate race, Mills has been the less talked about candidate. It’s an odd position for a well-vetted two-term governor.

Her diagnosis for why Maine Democrats have not been able to knock off Collins is straightforward: Past nominees have been “untested.” The GOP senator has never had to face a Democrat who has won statewide before. If Collins has won in part because of her deep history in the state, Mills matches her.

“Each of us probably knows everybody in Maine, one way or other,” Mills said in an interview.

Mills started as district attorney in rural, more conservative western Maine before being elected to the state legislature, then served as attorney general for much of Republican Paul LePage’s tenure as governor, frequently clashing with him. In 2018, she became the first gubernatorial candidate in Maine in 20 years to win the general election with at least 50 percent of the vote, as well as the state’s first female governor. Four years later, when LePage attempted a comeback, she beat him by 13 percentage points.

Governing with a Democratic trifecta, Mills expanded Medicaid and enacted a string of other priorities, including free community college, universal school meals and expanded abortion access following the Dobbs decision.

Since Trump’s return to office, Mills has faced off with him several times. In a White House confrontation last year, the president threatened to withhold funding from Maine over the state’s continued allowance of transgender participation in youth sports, Mills fired back: “See you in court.” The Trump administration paused certain agriculture department funding to Maine; the state sued and the money was restored.

The episode provided a theme that underlies the governor’s Senate campaign: Collins has not stood up to the president, but Mills will. Her latest TV ad describes her as “the one who took on Donald Trump and won.”

“Susan Collins is formidable,” said Trish Riley, a retired health policy expert who hosted Mills in her Brunswick home last month. “And the only person who can beat a formidable candidate is another formidable candidate, and that’s Janet.”

Mills’ tenure as governor has not been free from conflict with other Democrats. She at times disagreed with progressives in the legislature, issuing more than 50 vetoes, with the most prominent conflicts around labor and tribal sovereignty. That created openings for Platner to hit her record from the left, and his prominent endorsers have included several labor unions.

The bigger challenge for her in the primary may be the support from national Democrats like Schumer. Sara Gideon’s 2020 loss to Collins, despite strong national Democratic support which helped her far outspend the Republican, led to a sense in the state that the national Democratic actors did not use money wisely and did not understand Maine. For some, that distrust has only compounded since Trump returned to office.

“There’s a reaction among a lot of Democrats to what they see as the weakness of the establishment leaders in Washington,” said Amy Fried, a retired political science professor from the University of Maine and longtime Collins critic. “The fact that Chuck Schumer is the one who recruited Mills — maybe she would have run anyway, but he’s definitely associated with her. And then you have a lot of people who are on the Left who are really unhappy with what Democratic leadership has done when it comes to pushing back on Trump.”

Mills maintains that she made no promises to Schumer, and the decision to run was hers. She bristles at the idea that she would be considered part of the political establishment.

“I got elected to the legislature, not because somebody said, ‘You should be anointed to his job.’ I worked for it, I ran for it, and I won,” she said in an interview. “When I ran for district attorney, I defeated three guys for the primary, and then another guy for the general. Nobody ever gave it to me on a silver platter. Again, when I ran for governor: Seven-way primary. And I won. I’m used to that. Bring it on.”

Republicans have been gleeful at the prospect of a grueling primary.

“Maine Democrats are in a race of extreme vs more extreme — the only question is which of their candidates will run farther to the left to claim victory in this messy primary,” Republican National Committee spokesperson Kristen Cianci said in a statement.

Whoever prevails in June will have to take on the electorally resilient Collins. If Democrats fail to knock off the GOP senator, there will be recriminations from whichever side loses the primary that their candidate would have been able to defeat her.

Most supporters of Platner and Mills say they would back the eventual Democratic nominee regardless, with defeating Collins the most important priority. But a nasty primary could still risk alienating some voters, when every vote will count in November.

“The differences are really pretty big between the two candidates, and I think it’s probably going to get strongly oppositional towards the end,” said Cote, the former gubernatorial candidate. “And how the victor is going to unite the party afterwards is going to be a huge challenge.”