Janet Mills launches Senate bid to unseat Susan Collins as Graham Platner readies primary fight in Maine

Maine’s 2026 Senate landscape shifted decisively today as Gov. Janet Mills launched a campaign to unseat five-term Republican Sen. Susan Collins—immediately transforming a once-hypothetical contest into one of the cycle’s marquee fights. The announcement hardens Democratic hopes of flipping a seat in a state that has trended blue in federal contests, while adding new urgency to an already energized primary field led by insurgent Democrat Graham Platner, who is demanding a series of debates across the state.

Mills’ entry raises the stakes for Collins

Mills, 77, enters with unparalleled name recognition, a statewide organization, and a record of winning comfortably in Maine’s polarized politics. Her message is calibrated for a general election: defend reproductive rights, protect social programs, and confront the Trump-era agenda that Collins has at times enabled and at times resisted. Collins, 72, remains a disciplined campaigner with deep ties to local institutions and a reputation for bucking her party—assets that helped her survive the 2020 blue wave in Maine. But the presence of a popular, two-term governor at the top of the Democratic ticket means Collins faces her most formidable race in years.

Why it matters: This seat is one of the few realistic Republican-held targets on the 2026 map. If Democrats are to retake the Senate, Maine is near the top of the must-win list.

A contested Democratic primary, not a coronation

Mills does not clear the field. The Democratic primary has already been animated by Platner, a 41-year-old Marine and Army veteran and oyster farmer whose working-class, populist pitch has drawn large crowds and small-dollar momentum. Younger contenders like Jordan Wood have also argued for a generational shift. That makes the primary a proxy fight between experience and disruption—between an establishment favorite with governing chops and an outsider channeling grassroots frustration with both parties.

The age question: Mills would be the oldest freshman senator in modern history. Allies say her experience outweighs the optics; skeptics worry it blunts Democrats’ argument for renewal. In Maine—the nation’s oldest state by median age—overt age attacks risk backlash.

Platner turns up the heat: “Let’s debate—everywhere”

Within hours of Mills’ launch, Platner amplified his call for multiple debates and open forums, urging Democrats to take the argument to voters from Aroostook County to York. The demand is strategic: televised clashes would highlight contrasts on health care, unions, foreign policy, and the party’s relationship with big donors. It also plays to Platner’s strengths—retail politics, unscripted exchanges, and an authenticity-driven stump style that has helped him overperform expectations at town halls.

What debates could surface:

• Economics: Mills can tout bipartisan budgets and pandemic-era stabilization; Platner will push Medicare-for-all-style coverage, anti-monopoly action, and pro-labor reforms.

• Foreign policy: Expect sharper skepticism from Platner on military aid and overseas interventions, forcing Democrats to articulate a clear post-2024 doctrine.

• Party power: Platner frames the race as a choice between “movement” and “machine,” while Mills argues only a tested executive can actually beat Collins.

Collins’ playbook: moderation, money, and Maine-first

Collins will lean on three pillars. First, her centrist brand and seniority—especially her clout on Appropriations—allow her to claim tangible wins for local communities. Second, Republicans and allied groups have already banked significant resources to define Mills early and to paint the Democratic field as out of step on energy, spending, and immigration. Third, Collins’ coalition historically crosses party lines, particularly in the 2nd Congressional District, where ticket-splitting remains a live tradition.

Potential vulnerabilities: Roe v. Wade’s overturning continues to reshape suburban politics; Collins’ pivotal Kavanaugh vote will feature prominently in Democratic messaging. In an inflation-weary economy, however, Republicans see openings on taxes, heating costs, and regulation.

Early trajectories, key metrics to watch

• Polling volatility: Expect an initial Mills bounce in name ID; the more telling number will be Collins’ ceiling and whether undecideds break along party lines or by candidate image.

• Money and mechanics: Can Platner keep pace online and union-to-union while Mills consolidates institutional cash? Watch Q4 filings and local endorsement velocity.

• Debate calendar: If Platner’s debate push lands, the number, format, and location of forums will shape coverage and grassroots enthusiasm.

• Regional splits: Mills’ path runs through high-turnout coastal towns and Portland’s metro; Collins must defend northern and rural margins while limiting losses in the south.

Mills’ entry guarantees Susan Collins her sternest examination in a quarter century. Yet before Democrats can test Collins, they must resolve a sharp internal debate over message, messenger, and generation. Platner’s demand for frequent, statewide debates ensures that resolution won’t happen behind closed doors. If Democrats emerge united—and if Mills or a rival can keep Collins on defense—Maine could decide control of the Senate. If the primary turns costly and caustic, Collins’ vaunted resilience might be enough for one more escape.