“I’ve never backed down from a bully, and I never will,” Mills said in her launch video, which focused heavily on President Donald Trump. “Honestly, if this President and this Congress were doing things that were even remotely acceptable, I wouldn’t be running for the U.S. Senate. But when Trump rips away healthcare from millions of Americans and drives up costs on everything from groceries to housing to trucks and cars, then turns around and gives corporate CEOs a massive tax cut – and Susan Collins helps them do it after she helped him overturn Roe v. Wade – I hear my father’s voice saying, ‘Fight back. Janet.’”

As the only GOP senator serving in a state won by former Vice President Kamala Harris, Senate Democrats see Collins as the most vulnerable incumbent seeking reelection in the party’s quest to overcome an unfavorable midterm map and retake the majority.

But Collins has for decades fought off Republican and Democratic challengers, proving to be a formidable opponent as one of the most centrist and bipartisan members of the Senate. Her second-quarter campaign filings showed a steady stream of money from supporters, raising $2.4 million in the three-month period that ended with June and had $5.25 million cash on hand.

“I won’t sit idly by while Maine people suffer, and politicians like Susan Collins bend a knee as if this were normal,” she said. “My life’s work has prepared me for this fight, and I’m ready to win this election will be a simple choice.”

Mills, a top recruit of Senate Minority Leader Chuck Schumer (D-NY), is unable to seek a third consecutive term under Maine law but could seek a third nonconsecutive term in 2030.

She joins an already crowded field of other Democratic Senate hopefuls who are mostly political newcomers, including brewer Dan Kleban, oysterman Graham Platner, and former congressional aide Jordan Wood. Platner is endorsed by progressive Sen. Bernie Sanders (I-VT).

But with the support of Schumer and other national Democrats, as well as her political stature, Mills is considered the de facto frontrunner whose election and political experience buoy her party’s hopes to unseat Collins.

Mills preemptively announced her campaign last week before deleting a launch video and donation link that were posted. Currently 77 years old, she would be 79 when sworn in, marking the oldest freshman senator in U.S. history. Mills’s candidacy also tees up a generational clash in the party against several younger political newcomers vying for the nomination.

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Republicans sought to capitalize on what could be a messy primary, as well as Mills’s age, in their counter messaging.

“Maine Democrats are locked in a bruising fight between Chuck Schumer’s out-of-touch
establishment and Bernie Sanders’ far-left radicals,” said Joanna Rodriguez, the communications director for the National Republican Senatorial Committee. “Janet Mills wants to be the oldest freshman senator in American history after a record of failure that turned Maine into one of the weakest economies in New England. No matter which Democrat emerges, we’re confident Mainers will continue to trust independent problem solver Susan Collins to keep delivering for them.”