Maine Gov. Janet Mills plans to launch her long-anticipated U.S. Senate campaign next week, according to a person familiar with the governor’s plans.

The news was first reported by the national political news website Axios, which obtained internal documents showing Mills plans to launch her bid for the seat currently held by Republican Sen. Susan Collins on Tuesday.

But in an apparent misstep, Mills’ campaign preemptively announced her candidacy in several posts on social media Friday afternoon before quickly taking them down.

A spokesperson for Mills did not immediately respond Friday night to a request for an interview about the miscue.

Over the last several weeks, Mills, 77, has made numerous public appearances across the state touting her achievements as governor and saying she’s “seriously considering” a run. Last month, she said she would likely decide in November, but her timeline has moved up.

The governor, who is nearing the end of her second term, has been recruited by national Democrats, including Senate Minority Leader Chuck Schumer, to take on Collins, a five-term incumbent whom they consider to be vulnerable because of low approval ratings.

Mills’ entrance into the race sets up a primary with a growing number of Democrats looking to unseat Collins, who has held the seat since 1996 and now chairs the powerful Appropriations Committee.

Among them is Graham Platner, an oyster farmer from Hancock County whose campaign has generated considerable national media buzz and large crowds at a series of town hall events he’s been hosting. At an event in Brewer on Thursday, an estimated 650 people turned out.

Other candidates include Dan Kleban of Cumberland, co-founder of the Maine Beer Co.; Jordan Wood, a former congressional staffer from Bristol; Daira Smith-Rodriguez, a former Air Force civilian contractor from Biddeford; and David Costello, a Brunswick Democrat and former U.S. AID official who ran unsuccessfully last year against Sen. Angus King.

Independent Phil Rench of Waterboro, a former senior engineer for Elon Musk’s SpaceX, also has announced his candidacy.

Mills immediately becomes a front-runner for the Democratic nomination. She has high name recognition and has twice won statewide elections. She also has the backing of Schumer, who is under pressure to flip the Senate back to Democratic control and act as a check on President Donald Trump’s power.

“Party leaders, more than anything else, they want to win,” University of Maine political scientist Mark Brewer told the Press Herald last month. “They’re going to back the (candidate) that gives them the best chance of winning.”

Many national Democrats still see Mills as the best option to beat Collins, and there is a long history of sitting or recent governors running for Senate. According to Ballotpedia, a nonpartisan online political encyclopedia, 62 governors have run since 1986. Of those, 45% have won, 35% have lost in the general election and 19% have lost in primaries.

Mills has been critical of Trump’s policies this year, including during a high-profile exchange at the White House in February, when the president challenged her over whether Maine would comply with his directive banning transgender athletes from competing in sports. Mills responded by saying “see you in court.” Indeed, Maine has signed on to nearly three dozen lawsuits challenging the administration.

As Mills has flirted with a Senate run, others have pressured her to stay out of the race, including independent Sen. Bernie Sanders of Vermont. Sanders already has endorsed Platner and appeared alongside him at a rally in Portland on Labor Day.

Platner’s campaign also has been highlighting numerous opinion pieces and letters to the editor in local papers from people who don’t think Mills should run.

The field of Democrats is large, but it’s too early to tell how many will be viable by next June’s primary. Some of that will depend on candidates’ ability to raise money.

Platner announced this week that his campaign has raised $4 million so far. That, coupled with attendance at recent events, suggests he has staying power. But Wood also has raised a large sum, approximately $3 million through Sept. 30. The other candidates have not released their campaign fundraising totals and the Federal Election Commission deadline isn’t until next week.

Wood, 35, and Platner, 40, are a full generation younger than Mills, which means the Democratic primary here in Maine could figure prominently in the national conversation over the party’s future in the wake of Trump’s election in 2024.

Collins, meanwhile, remains a formidable candidate despite her perceived vulnerability. During her last reelection campaign, she easily defeated former Maine House Speaker Sara Gideon of Freeport in a race many expected to be closer.