Governor Janet Mills is officially kicking off her campaign for the U.S. Senate, joining a crowded primary field vying to challenge longtime Republican Senator Susan Collins next year.

She initially said she would make a decision by November, before news sources reported last week that she would announce her run this week, likely today

Mills has sparred with President Donald Trump’s administration since January and is framing her run as an effort to check the White House.

She enters a Democratic field that includes oysterman and veteran Graham Platner, and former congressional staffer Jordan Wood.

Another Democrat in the race, Maine Beer Company co-founder Dan Kleben, dropped out of the race on Tuesday and endorsed Gov. Mills.

National Democrats have been trying to recruit Mills, who at 77, would be the oldest freshman senator ever if elected.

Democrats see the Maine Senate race as one of their few opportunities to flip a Senate seat and chip away at the 53-seat Republican majority next year.

Mills is term limited as governor, having been elected twice in 2018 and 2022. She notably defeated former Republican Governor Paul LePage for her second term.

Mills is scheduled to speak alongside Maine lawyers at a public forum on Tuesday night that discusses standing up for the rule of law and how to save it.

The public forum will be held at the University of Southern Maine’s Hannaford Hall in Portland at 7 p.m.