Maine Gov. Janet Mills joined her state’s crowded Democratic Senate primary as the establishment favorite on Tuesday, aiming to flip Republican Sen. Susan Collins’ seat in a pivotal midterm year.

Democrats view the seat as one of their top pickup opportunities — the only in a state Kamala Harris won in 2024 — and Mills is among a few top-tier candidates Senate Minority Leader Chuck Schumer aggressively recruited to run this cycle. But first the term-limited governor must contend with a competitive primary against breakout candidate Graham Platner, an oyster farmer who announced he has more than $3 million in the bank and already received the endorsement of Sen. Bernie Sanders (I-Vt.).

Maine Beer Company owner Dan Kleban is also running for the nomination and his fundraising figures will be made public Wednesday, when federal filings are released.

In her launch video, Mills highlighted her recent fight with President Donald Trump over transgender sports and accused Collins of enabling him. “I won’t sit idly by while Maine people suffer and politicians like Susan Collins bend the knee as if this were normal,” Mills said.

Despite initial hesitation, the governor started interviewing staff and telling local reporters she was seriously considering a bid last month.

She addressed that long contemplation in her announcement, saying in the video, “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.”

The race sets up the latest generational clash for a party struggling to find its footing after losing the White House and both branches of Congress last year.

Mills, who won her seat by wide margins in her last two races, is 77 years old, making her five years Collins’ senior at a time when Americans are grappling with debates about the age of their politicians. If elected, she would be the oldest first-year senator ever. Platner is 41 and unlikely to leave the race for Mills; Kleban, who is 48, has so far dodged questions about what he would do if Mills jumped in.

Democrats need to pick up four seats in order to win back control of the Senate, a difficult task that all but has to include a pickup in Maine, where Harris won by 7 points.

Democrats poured millions of dollars into an ultimately-unsuccessful effort to unseat Collins in 2020 — but her declining popularity in the bluing state is giving Democrats hope that next year’s race could be their best chance yet.

Republicans are eager to expose Mills’ weaknesses, and have already targeted her public fight Trump, as well as her age.