The Race to Unseat Susan Collins: Maine's Democratic Primary Is Getting Ugly
An oyster farmer with Bernie Sanders's endorsement is crushing the sitting governor in primary polls. Susan Collins is sitting back with $10 million in the bank. And control of the Senate may depend on which Democrat survives.
Maine's Senate race is the single best pickup opportunity Democrats have on the 2026 map, and they might be about to blow it — not by losing to Susan Collins, but by destroying each other first. The June 9 Democratic primary has become a proxy war between the party establishment and its progressive wing, with two flawed candidates spending millions attacking one another while the five-term Republican incumbent barely lifts a finger.
On one side: Governor Janet Mills, 78, the establishment pick backed by Senate Minority Leader Chuck Schumer and the DSCC. She entered the race in October 2025 pledging to serve only one term. She has a track record of winning statewide and the institutional support of the party apparatus. But her age draws scrutiny, her close coordination with the DSCC has generated allegations of favoritism, and her fundraising has lagged badly.
On the other side: Graham Platner, 41, an oyster farmer, Iraq and Afghanistan combat veteran, and former private military contractor who launched a progressive insurgent campaign backed by Bernie Sanders, the UAW, and the Maine State Nurses Association. He's outraised both Mills and Collins this year. He leads Mills by 38 points in primary polls. And his "outsider" brand has electrified progressive voters in a state where the party establishment is increasingly unpopular.
Collins: The Survivor
Susan Collins has been counted out before. In 2020, polls showed her losing to Sara Gideon by as much as 12 points. She won by 9. She has survived every wave election since her first win in 1996, including blue waves in 2006, 2012, and 2018. She chairs the Senate Appropriations Committee — the ultimate bring-home-the-bacon position. And she has $10 million in cash on hand while spending almost nothing, because the Democrats are doing her work for her.
But 2026 is different. She's now the only Republican senator in any state that Kamala Harris won in 2024 — the last true cross-party outlier in the chamber. Maine voted for Biden by 9 points in 2020 and Harris by 7 in 2024. The trend line is against her. Seventy-one percent of Mainers say she doesn't deserve another term. Her approval ratings are underwater. And unlike Gideon in 2020, both Mills and Platner are genuinely "from Maine" — neutralizing the carpetbagger attacks Collins used so effectively last time.
"This is the first time I've ever found myself saying Susan Collins is in big trouble, and part of it is people are actually tired of her — and not just Democrats."
Alan Caron, Maine political consultantThe Primary: Establishment vs. Insurgent
The Platner-Mills contest mirrors a tension playing out across the Democratic Party nationally. Mills represents the theory that electability matters more than ideology — she's won statewide twice, she's a known quantity, she'll consolidate moderates. Platner represents the counter-theory: that Democrats lose when they nominate safe, institutional candidates, and that only a populist outsider can motivate the base and attract disaffected voters.
The polls have been decisive. Multiple surveys show Platner leading Mills by enormous margins among Democratic primary voters. Mills started running attack ads in March highlighting Platner's controversies — including past comments about sexual assault in the military — but stopped purchasing airtime by April, leading to rumors she might withdraw. Her campaign denied it, insisting they're "full steam ahead."
Platner has endorsements from Senators Sanders, Gallego, and Heinrich, plus major labor unions. Mills has Schumer, Cortez Masto, and the DSCC. The June 9 primary will use ranked-choice voting, with former 2024 nominee David Costello also on the ballot.
The Money Race
Platner outraised Collins and Mills in Q1 2026. But he's also spending heavily — $5 million spent against $4 million raised, leaving him with $2.7 million COH. Collins has $10 million banked and has barely spent a dime. Meanwhile, One Nation (a dark money group allied with Senate Republicans) has already dropped $10 million in "issue ads" boosting Collins. The general election will be expensive.
What Matters in November
Whoever wins the primary faces a formidable opponent. Collins has institutional advantages — the Appropriations chairmanship, nearly 30 years of constituent service, a brand built on independence from her party. She voted against some of Trump's nominees and against the GOP mega-bill's social spending cuts. Those votes give her cover with moderate voters.
But the political environment is toxic for Republicans nationally, and Collins can't run from her party affiliation. Maine isn't the ticket-splitting haven it used to be. If Democrats nominate a candidate who can unify the party after a bruising primary — and that's a big if — this race is a genuine toss-up heading into the fall.
Sabato's Crystal Ball, Cook Political Report, and Inside Elections all rate this race Toss-Up. It's one of only four Senate races nationally with that designation, alongside Michigan, Ohio, and North Carolina. Control of the Senate may ultimately run through this small, politically quirky New England state.